Cystic Fibrosis, CFTR Gene Variants, and Aspergillosis

Last reviewed: 8 April 2026

Some people with aspergillosis are told they have cystic fibrosis (CF), or that they carry a CFTR gene variant. This can be unexpected and may raise concerns about whether this explains their symptoms or diagnosis.

This article explains how cystic fibrosis and CFTR gene variants relate to Aspergillus-related lung disease, what current research shows, and—importantly—what conclusions should not be drawn.

Contents

Key points

  • Most people with aspergillosis do not have cystic fibrosis.
  • Most people with cystic fibrosis do not develop ABPA or CPA.
  • ABPA is linked to mucus and immune responses, not just infection.
  • CFTR variants may contribute to risk in some people, but are usually only one factor.
  • CPA is mainly driven by structural lung damage, not CFTR genetics.

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Important reassurance

Most people with aspergillosis do not have cystic fibrosis, and most people with cystic fibrosis do not develop Aspergillus-related disease.

Although these conditions can overlap, they are usually separate. Genetic findings such as CFTR variants should be interpreted carefully and in context.

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What is cystic fibrosis?

Cystic fibrosis is a genetic condition caused by changes in the CFTR gene. This gene regulates salt and water movement across cells.

When CFTR function is reduced:

  • mucus becomes thick and sticky
  • airways are harder to clear
  • microorganisms persist more easily

This creates an environment where bacteria and fungi can accumulate over time.

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What is a CFTR gene variant?

CFTR variants range from severe mutations (causing cystic fibrosis) to mild or uncertain variants.

Carriers (with one variant):

  • are common in the general population
  • usually have no symptoms
  • may have subtle effects in some cases

These subtle effects may include reduced mucus clearance or increased susceptibility to airway inflammation.

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How CFTR affects the lungs

CFTR dysfunction affects the lungs in several key ways:

  • Mucus dehydration: mucus becomes thick and difficult to clear
  • Impaired clearance: particles and microbes remain in the airways
  • Chronic inflammation: immune responses become exaggerated

This combination creates a “retention environment” where inhaled organisms—including Aspergillus—may persist.

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How Aspergillus behaves in the lungs

Aspergillus is inhaled by everyone, but its effects vary depending on the lung environment.

  • Healthy lungs: spores are cleared
  • Impaired clearance: spores may persist
  • Sensitive immune system: allergic reactions may develop
  • Damaged lungs: chronic infection may develop

This explains why Aspergillus-related disease is diverse and depends heavily on underlying lung conditions.

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ABPA and cystic fibrosis

ABPA is an allergic immune reaction to Aspergillus.

It is recognised in cystic fibrosis because:

  • mucus retention increases exposure to Aspergillus
  • immune responses can be exaggerated

However:

  • Many CF patients never develop ABPA
  • Most ABPA patients do not have CF

Some studies suggest CFTR variants may increase susceptibility, but this is not consistent across all research.

Key message: ABPA and CF can overlap, but one does not imply the other.

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CPA and cystic fibrosis

CPA is a chronic fungal infection that develops in structurally damaged lungs.

The most important risk factor is:

pre-existing lung damage

This includes:

  • bronchiectasis
  • previous tuberculosis
  • COPD

Cystic fibrosis can lead to bronchiectasis, and therefore indirectly increase CPA risk.

However:

  • CPA is rarely driven directly by CFTR genetics
  • most CPA patients do not have CF

Key message: CPA is primarily a disease of lung structure, not genetics.

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Modern CF treatments and Aspergillus

CFTR modulators (such as elexacaftor/tezacaftor/ivacaftor) have transformed CF care.

They:

  • improve CFTR function
  • thin mucus
  • improve clearance

Studies suggest:

  • reduced Aspergillus detection in some patients
  • fewer ABPA exacerbations in some cases

However:

  • ABPA still occurs
  • existing lung damage remains
  • immune responses are not fully corrected

Overall: these therapies improve risk but do not eliminate Aspergillus-related disease.

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Does a CFTR variant explain symptoms?

No single factor explains complex lung disease.

Symptoms may result from:

  • underlying lung disease
  • infection
  • inflammation
  • environmental exposure

A CFTR variant may contribute, but is rarely the sole cause.

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What should patients take from this?

  • CF and CFTR variants can sometimes contribute
  • ABPA has the strongest connection
  • CPA is mainly driven by lung damage
  • Most patients with aspergillosis do not have CF

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When to seek medical advice

Seek advice if symptoms worsen, change, or include coughing up blood, fever, or chest pain.

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Conclusion

Cystic fibrosis and CFTR gene variants can play a role in some patients with Aspergillus-related lung disease, particularly where mucus clearance is affected. However, they should not be overemphasised. In most cases, they are just one part of a broader clinical picture involving lung structure, immune response, and environmental exposure.

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References

This article is for general information and does not replace advice from your clinical team.

by GAtherton

Asthma and Aspergillosis

How fungal spores interact with asthma and other lung diseases

Every day we inhale thousands of microscopic fungal spores from the environment. One of the most common fungi in the air is Aspergillus fumigatus. In healthy lungs these spores are removed quickly by the lungs’ natural defence systems and cause no illness.

However, in people with asthma—particularly severe asthma—the interaction between the lungs and Aspergillus can be very different. The fungus may trigger allergic inflammation, grow in mucus within the airways, or occasionally contribute to chronic lung disease.

Understanding this relationship helps explain several important conditions including:

  • Aspergillus sensitisation

  • Severe Asthma with Fungal Sensitisation (SAFS)

  • Allergic Bronchopulmonary Aspergillosis (ABPA)

  • Aspergillus bronchitis

  • Chronic Pulmonary Aspergillosis (CPA)

Although asthma is the most common condition linked to Aspergillus allergy, other lung diseases such as bronchiectasis, Chronic Obstructive Pulmonary Disease (COPD), and tuberculosis-related lung damage can also create environments where the fungus becomes important.

Why Asthma Creates a Favourable Environment for Aspergillus

Asthma is a disease of airway inflammation and hyper-reactivity. The bronchi narrow during attacks because the airway wall becomes swollen and the surrounding smooth muscle contracts.

Several features of asthma make it easier for Aspergillus spores to remain in the lungs.

Mucus production

Asthma often causes increased production of thick airway mucus.

Normally mucus traps inhaled particles and moves them upward toward the throat via the mucociliary escalator.

In asthma:

  • mucus becomes thicker

  • clearance becomes less efficient

  • spores remain trapped

This trapped environment allows fungal spores to persist in the airway mucus.

Allergic immune responses

Many asthma patients have Type-2 (T2) inflammation (50-70%), involving immune pathways driven by:

  • Immunoglobulin E (IgE)

  • Interleukin-4

  • Interleukin-5

  • Interleukin-13

  • eosinophils

These pathways respond strongly to fungal allergens. When the immune system recognises Aspergillus proteins it may trigger allergic inflammation in the airways.

Fungal sensitisation is increasingly recognised as an important contributor to severe asthma (PMID: 24735832).

Aspergillus Sensitisation

Many people with asthma develop allergic sensitisation to Aspergillus.

Sensitisation means the immune system produces antibodies against fungal proteins.

Features include:

  • positive Aspergillus skin test or IgE blood test

  • worsening asthma symptoms

  • increased exacerbations

Studies suggest 10–25% of patients attending severe asthma clinics show Aspergillus sensitisation (PMID: 24735832).

However, sensitisation alone does not necessarily cause lung damage.

Severe Asthma with Fungal Sensitisation (SAFS)

Some patients with severe asthma have fungal sensitisation but do not meet the criteria for ABPA.

This condition is known as Severe Asthma with Fungal Sensitisation (SAFS).

Typical features include:

  • severe or poorly controlled asthma

  • fungal allergy

  • moderate IgE elevation

A randomised controlled trial demonstrated that antifungal therapy may improve symptoms in some SAFS patients (PMID: 18948425).

Allergic Bronchopulmonary Aspergillosis (ABPA)

Allergic Bronchopulmonary Aspergillosis is the most important Aspergillus-related disease associated with asthma.

ABPA occurs when Aspergillus grows within airway mucus and triggers a strong allergic immune response.

Typical findings include:

  • very high total IgE levels

  • Aspergillus-specific IgE and IgG antibodies

  • eosinophilia

  • mucus plugs containing fungal hyphae

  • central bronchiectasis

ABPA occurs in approximately:

  • 1–2% of all asthma patients

  • up to 10–15% of severe asthma patients

These figures come from global prevalence estimates of ABPA in asthma populations (PMID: 23210682/.

Modern diagnostic criteria for ABPA were updated by the International Society for Human and Animal Mycology (ISHAM) in 2024 (PMID: 38423624).

Asthma and Aspergillus Disease Pathway


Possible interactions between asthma and Aspergillus. Some patients develop allergic disease (ABPA) which may lead to airway damage such as bronchiectasis (NB Progression to CPA is very rare).

When ABPA Causes Bronchiectasis

Repeated inflammation from ABPA may damage airway walls and lead to bronchiectasis.

Bronchiectasis occurs when airways become:

  • permanently widened

  • distorted

  • unable to clear mucus effectively

Instead of being cleared from the lungs, mucus pools in the airways.

This retained mucus creates an environment where microorganisms—including fungi—can grow.

Aspergillus Bronchitis

In some patients with bronchiectasis or chronic lung disease, Aspergillus may persist in airway mucus and cause chronic airway infection rather than allergy.

Symptoms may include:

  • chronic cough

  • sputum production

  • repeated positive Aspergillus cultures

IgE levels are usually lower than in ABPA.

Chronic Pulmonary Aspergillosis (CPA)

Chronic Pulmonary Aspergillosis is a slowly progressive fungal infection of damaged lung tissue.

CPA usually develops in lungs containing:

  • cavities

  • severe structural damage

Common underlying diseases include:

  • tuberculosis

  • sarcoidosis

  • severe COPD

Globally, the most common cause of CPA is previous tuberculosis infection (PMID: 22271943).

Asthma alone rarely causes CPA, but severe bronchiectasis or ABPA-related lung damage may occasionally lead to it.

Aspergillosis and Immune Competence

Different forms of aspergillosis occur depending on lung damage and immune function.

Other Lung Diseases Linked to Aspergillus

Although asthma is the most common condition associated with Aspergillus allergy, several other lung diseases can predispose to fungal disease.

Bronchiectasis

Dilated airways trap mucus, allowing fungi and bacteria to persist.

COPD

Chronic airway inflammation may lead to Aspergillus bronchitis or chronic pulmonary aspergillosis.

Tuberculosis

Post-tuberculosis lung cavities are the most common global cause of chronic pulmonary aspergillosis (PMID: 22271943).

Key Messages

  • Asthma is one of the most important diseases associated with Aspergillus-related lung conditions.

  • Many asthma patients develop fungal sensitisation.

  • A smaller proportion develop Allergic Bronchopulmonary Aspergillosis (ABPA).

  • Repeated inflammation from ABPA can lead to bronchiectasis.

  • Chronic pulmonary aspergillosis is rare in asthma alone but may occur if significant lung damage develops.

Understanding these interactions helps guide diagnosis and treatment for people living with asthma and Aspergillus-related disease.

Further reading

Agarwal R, Chakrabarti A, Shah A, Gupta D, Meis JF, Guleria R, Moss R, Denning DW; ABPA complicating asthma ISHAM working group. Allergic bronchopulmonary aspergillosis: review of literature and proposal of new diagnostic and classification criteria. Clin Exp Allergy. 2013 Aug;43(8):850-73. doi: 10.1111/cea.12141. PMID: 23889240.

Denning DW, Pleuvry A, Cole DC. Global burden of chronic pulmonary aspergillosis as a sequel to pulmonary tuberculosis. Bull World Health Organ. 2011 Dec 1;89(12):864-72. doi: 10.2471/BLT.11.089441. Epub 2011 Sep 27. PMID: 22271943; PMCID: PMC3260898.

by GAtherton

Looking further into the future - could we control lung damage, preserve healthy lung tissue better?

Can Lungs Repair Themselves?

What New Research Means for People with CPA (and Other Aspergillosis)

A recent scientific discovery has helped researchers understand how certain lung cells decide whether to focus on repairing damage or defending against infection. The work, highlighted by the Mayo Clinic and published in Nature Communications, describes a molecular “switch” inside specialised lung cells that influences this balance.

For people living with Chronic Pulmonary Aspergillosis (CPA) — and also those with Allergic Bronchopulmonary Aspergillosis (ABPA) — this kind of research is relevant. But it needs careful explanation.

This is not about rebuilding destroyed lungs.
It is about understanding how to better protect and preserve the lung tissue that remains.

The Discovery: A “Repair vs Defence” Switch

Researchers identified a regulatory circuit in alveolar type II (AT2) cells — specialised cells that:

  • Produce surfactant (which keeps air sacs open)

  • Act as a reserve “repair” population in the lung

  • Can regenerate other essential lung cells after injury

The study showed that these cells operate under tight control. When infection is present, they prioritise defence. When injury needs healing, they can switch into repair mode.

The key insight is that this switch is biologically regulated. It is not random. That means, in theory, it may one day be possible to influence it.

What “Repair” Means — and What It Does Not Mean

When we talk about lung repair in this context, we must be very clear.

It does not mean:

  • Lung cavities caused by CPA will close in the foreseeable future

  • Established fibrosis will melt away

  • Bronchiectasis will reverse

  • Severely distorted lung architecture will rebuild

CPA cavities represent major structural remodelling — destruction of alveoli, scarring, altered blood supply, and thickened pleura. Reconstructing that complex architecture is biologically extremely challenging and not currently realistic within the next decade.

What repair does realistically mean

In chronic lung disease, “repair” is more likely to mean:

  • Supporting survival of remaining alveoli

  • Preventing excessive fibrotic signalling

  • Helping lung lining cells recover more efficiently after inflammation

  • Reducing cumulative injury from repeated infection

  • Slowing progression of structural change

In other words:

Not rebuilding what is gone — but better protecting what remains.

For many people with CPA, this is a crucial distinction.

Why Preservation Is a Major Goal in CPA

CPA usually develops in lungs already weakened by conditions such as tuberculosis, non-tuberculous mycobacteria, chronic obstructive pulmonary disease, or severe pneumonia.

Over time, CPA can lead to:

  • Expanding cavities

  • Progressive scarring

  • Reduced gas exchange

  • Reduced exercise tolerance

Many patients have limited lung reserve. Even small additional losses of functioning lung tissue can significantly increase breathlessness or fatigue.

If future therapies could slow the rate of progression — even modestly — that would meaningfully affect long-term outcomes.

Flattening the decline curve is not trivial. It changes quality of life.

Why This Also Matters in ABPA

In ABPA, repeated inflammatory episodes can lead to:

  • Airway remodelling

  • Mucus plugging

  • Development or progression of bronchiectasis

Better control of inflammatory signalling — combined with improved epithelial recovery — could reduce long-term airway damage.

Again, this is about preservation rather than reversal.

Where Development Has Reached

The current research is still laboratory-based. It used advanced techniques such as:

  • Single-cell sequencing

  • Imaging of lung tissue

  • Preclinical models of injury

No human treatments based on this discovery are yet available.

However, the significance lies in identifying:

  • A defined molecular pathway

  • A controllable regulatory mechanism

  • A clearer understanding of why repair fails in chronic inflammation

That foundational knowledge is what eventually allows targeted drug development.

The Balance Challenge in Aspergillosis

There is an additional complexity in fungal lung disease.

Any attempt to promote repair must not weaken antifungal defence.

The immune system must:

  • Control Aspergillus

  • Avoid causing excessive inflammatory damage

Future therapies would need to strike that balance carefully.

What This Means for Patients Now

This discovery does not change current treatment.

The most effective preservation strategies today remain:

  • Consistent antifungal therapy when indicated

  • Careful inflammatory control

  • Biologic therapies where appropriate

  • Airway clearance

  • Vaccination and infection prevention

  • Avoiding damp and mould exposure

  • Pulmonary rehabilitation

These measures are already forms of lung preservation.

A Realistic and Hopeful Perspective

It is unlikely that cavities from CPA will be repaired in the near future.

It is realistic that within the next 5–10 years we may see improved strategies aimed at:

  • Slowing structural progression

  • Supporting endogenous repair cells

  • Reducing fibrotic signalling

  • Improving recovery after exacerbations

For people living long-term with CPA or ABPA, even incremental preservation could significantly affect independence and quality of life.

The science is still early — but understanding how the lung decides to repair itself is an important step forward.

Reference

Sawhney, A.S., Deskin, B.J., Cai, J. et al. A molecular circuit regulates fate plasticity in emerging and adult AT2 cells. Nat Commun 16, 8924 (2025). https://doi.org/10.1038/s41467-025-64224-1

by GAtherton

🧬 How Biologics Are Reshaping Our Understanding of ABPA Subtypes

For many years, Allergic Bronchopulmonary Aspergillosis (ABPA) was viewed as a single condition:

An allergic reaction to Aspergillus fumigatus in the lungs, treated primarily with steroids and sometimes antifungal medication.

Biologic therapies are changing that picture.

They are not just new treatments — they are helping us understand that ABPA may not be one uniform disease, but a spectrum of related inflammatory patterns.

🧠 The Traditional View of ABPA

Historically, ABPA has been defined by:

  • Asthma (or cystic fibrosis)

  • High total IgE

  • Sensitisation to Aspergillus

  • Raised eosinophils

  • Characteristic CT changes (e.g. bronchiectasis, mucus plugging)

The dominant biological explanation was:

A Type 2 (allergic) immune overreaction driven by eosinophils and IgE.

Steroids were used to suppress this immune response.

This model assumed that most patients had broadly similar immune drivers.

💊 What Are Biologics?

Biologics are targeted antibody therapies designed to block specific immune pathways.

In asthma and ABPA, the main targets are:

  • IL-5 (drives eosinophils)

  • IL-5 receptor

  • IL-4 / IL-13 (drive allergic inflammation)

  • IgE

Examples include:

  • Anti–IL-5 therapies (e.g. mepolizumab, benralizumab)

  • Anti–IL-4/IL-13 therapy (e.g. dupilumab)

  • Anti-IgE therapy (e.g. omalizumab)

Instead of broadly suppressing immunity like steroids, they selectively block parts of the allergic pathway.

🔍 What Biologics Are Teaching Us

As biologics have been used in ABPA (often off-label or in specialist centres), an interesting pattern has emerged:

Not all ABPA behaves the same way.

Some patients respond dramatically to anti–IL-5 therapy.
Others respond better to anti–IL-4/IL-13 therapy.
Some show strong IgE-driven disease.
Others appear more mucus-dominant.

This suggests that ABPA may include different inflammatory endotypes (biological subtypes), even if outward symptoms look similar.

🧩 Possible Emerging ABPA Subtypes

While research is ongoing, clinicians are beginning to recognise patterns such as:

1️⃣ Strongly Eosinophilic-Dominant ABPA

  • Very high eosinophils

  • Frequent exacerbations

  • Often responds well to IL-5 blockade

2️⃣ IgE-Heavy Allergic ABPA

  • Extremely high total IgE

  • Prominent allergic features

  • May respond to anti-IgE therapy

3️⃣ Mucus-Plug Dominant ABPA

  • Recurrent thick mucus impaction

  • Radiological plugging

  • May involve additional inflammatory drivers

4️⃣ Steroid-Dependent ABPA

  • Relapses when steroids reduced

  • Biologics may allow steroid-sparing strategies

These patterns are not yet formal categories, but biologics are revealing that ABPA is biologically more complex than once thought.

🧪 Blood Eosinophils vs Airway Inflammation

Biologics have also highlighted another key insight:

Blood eosinophil levels do not always perfectly reflect what is happening in the lungs.

Some patients:

  • Have modest blood eosinophils

  • But still show eosinophilic airway activity

Biologic response patterns are helping refine how we interpret these markers.

🧠 Moving From “Diagnosis” to “Endotype”

Traditionally, medicine focused on:

Diagnosis (ABPA vs not ABPA)

Biologics are pushing us toward:

Endotype (which immune pathway is dominant in this patient?)

This matters because targeted therapy works best when matched to the dominant pathway.

In future, ABPA may be classified not just by clinical features, but by molecular drivers.

🫁 What This Means for Patients

Biologics offer:

  • Reduced steroid dependence

  • Fewer exacerbations

  • Improved lung function in selected patients

  • Potential improvement in mucus burden

But they also help answer deeper questions:

  • Why do some patients relapse frequently?

  • Why do some have extreme eosinophilia?

  • Why do others have more mucus plugging than inflammation?

They are helping personalise ABPA care.

⚖ Important Caveats

  • Biologics are not currently licensed specifically for ABPA in many countries.

  • Evidence is growing but still developing.

  • They are usually considered in specialist centres.

  • They are not appropriate for every patient.

Steroids and antifungals remain core treatments.

🔭 The Future

Over the next decade, we may see:

  • Better classification of ABPA subtypes

  • Biomarker-guided treatment selection

  • Reduced long-term steroid exposure

  • Improved understanding of mucus plug biology

  • Trials specifically designed for ABPA (rather than extrapolated from asthma)

Biologics are not just new drugs.

They are acting as scientific tools that are reshaping how we think about ABPA itself.

🧠 Key Takeaway

ABPA is no longer seen as one single uniform allergic condition.

Biologic therapies are revealing that:

ABPA is likely a spectrum of related inflammatory patterns — and treatment may increasingly be tailored to the dominant pathway in each individual.

References

Agarwal R, Sehgal IS, Muthu V, Denning DW, Chakrabarti A, Soundappan K, Garg M, Rudramurthy SM, Dhooria S, Armstrong-James D, Asano K, Gangneux JP, Chotirmall SH, Salzer HJF, Chalmers JD, Godet C, Joest M, Page I, Nair P, Arjun P, Dhar R, Jat KR, Joe G, Krishnaswamy UM, Mathew JL, Maturu VN, Mohan A, Nath A, Patel D, Savio J, Saxena P, Soman R, Thangakunam B, Baxter CG, Bongomin F, Calhoun WJ, Cornely OA, Douglass JA, Kosmidis C, Meis JF, Moss R, Pasqualotto AC, Seidel D, Sprute R, Prasad KT, Aggarwal AN. Revised ISHAM-ABPA working group clinical practice guidelines for diagnosing, classifying and treating allergic bronchopulmonary aspergillosis/mycoses. Eur Respir J. 2024 Apr 4;63(4):2400061. doi: 10.1183/13993003.00061-2024. PMID: 38423624; PMCID: PMC10991853.

by GAtherton

🧬 Could Antibody-Driven Dissolving of Charcot–Leyden Crystals Help ABPA?

Researchers have recently discovered that Charcot–Leyden crystals (CLCs) — the needle-shaped structures formed from the eosinophil protein galectin-10 — are not just debris.

In laboratory studies, specially designed antibodies can dissolve these crystals.

This has raised two important questions:

  1. Could dissolving the crystals reduce airway inflammation?

  2. Could dissolving them make mucus plugs easier to clear?

Here is what we currently know.

1️⃣ Could dissolving crystals reduce airway inflammation?

What we know

Laboratory and animal studies have shown:

  • Charcot–Leyden crystals can activate immune cells (especially macrophages).

  • They can stimulate inflammatory pathways (including inflammasome signalling).

  • In mouse models, antibodies targeting galectin-10 dissolved the crystals.

  • When crystals were dissolved, airway inflammation decreased.

This suggests that the crystals themselves may amplify inflammation, rather than simply mark it.

What this means biologically

In ABPA and eosinophilic asthma:

  • Eosinophils release galectin-10.

  • Galectin-10 crystallises.

  • Crystals may trigger further immune activation.

  • That leads to more inflammation → more eosinophils → more crystals.

Dissolving the crystals could theoretically interrupt this feedback loop.

How likely is this to help inflammation in humans?

Moderately plausible, but not yet proven.

The biological mechanism is strong.
The animal data are encouraging.
But no human clinical trials have yet shown reduced inflammation through crystal dissolution.

If developed successfully, this approach could:

  • Reduce airway immune activation

  • Lower exacerbation risk

  • Potentially reduce steroid dependence

But at present, it remains investigational.

2️⃣ Could dissolving crystals make mucus plugs easier to cough up?

This is more speculative — but still biologically reasonable.

Why mucus plugs are so thick in ABPA

ABPA mucus plugs contain:

  • Gel-forming mucins

  • DNA from inflammatory cells

  • Dead cells

  • Fungal fragments

  • Eosinophil proteins

  • Charcot–Leyden crystals

The crystals are:

  • Rigid

  • Needle-shaped

  • Structurally stable

When embedded in mucus, they likely increase:

  • Mechanical stiffness

  • Plug density

  • Resistance to deformation

From a physics perspective:

Removing rigid crystalline structures from a gel should reduce stiffness and improve flow.

Do we have direct evidence?

No.

There are currently:

  • No human studies measuring mucus clearance after crystal dissolution

  • No trials showing improved plug expectoration from crystal-targeting therapy

So while it is plausible that dissolving crystals could soften plugs, this has not yet been demonstrated in patients.

3️⃣ How strong is the overall case?

Outcome Evidence strength Likelihood
Reduced inflammation Strong biological rationale + animal data Moderately promising
Easier mucus clearance Biophysical plausibility only Possible but unproven

Inflammation reduction is the more evidence-supported target.
Improved plug clearance is plausible but currently theoretical.

4️⃣ How does this compare to existing treatments?

Current therapies (e.g., anti-IL-5 biologics) reduce eosinophils upstream.

That leads to:

  • Less galectin-10 release

  • Fewer crystals forming

  • Reduced inflammation

  • Often improved mucus plugging

So biologics already indirectly reduce crystal burden.

A crystal-dissolving antibody would act downstream, targeting the structural product directly.

This could theoretically:

  • Accelerate resolution of existing plugs

  • Reduce residual inflammatory signalling

But again, this remains in early research stages.

5️⃣ Practical take-home message

At present:

  • Dissolving Charcot–Leyden crystals reduces inflammation in animal models.

  • It is biologically plausible that this could also soften mucus plugs.

  • There is no human clinical proof yet.

  • No approved therapy currently targets the crystals directly.

The concept is scientifically credible — but still under development.

🔭 The Bigger Picture

ABPA is increasingly understood as a condition driven by:

  • Eosinophils

  • Allergic immune signalling

  • Abnormal mucus biology

  • Structural plug formation

Crystal-targeting therapies may eventually become part of a more precise approach to treating eosinophilic airway disease.

But for now, they remain a promising research direction rather than a clinical option.

by GAtherton

🔬 Charcot–Leyden Crystals in ABPA and Asthma

What are they? Why do they form? Do they matter?

If you live with Allergic Bronchopulmonary Aspergillosis (ABPA) or severe asthma, you may see the term Charcot–Leyden crystals in a sputum or pathology report.

They can sound worrying.

They are:

  • Not fungus

  • Not infection

  • Not cancer

They are a sign of a particular type of allergic inflammation in the airways.

🧬 What Are Charcot–Leyden Crystals?

Charcot–Leyden crystals are microscopic, needle-shaped structures found in mucus.

They are made from a protein called galectin-10, which is stored inside a type of white blood cell called an eosinophil.

Eosinophils are immune cells involved in:

  • Allergic asthma

  • ABPA

  • Severe asthma with fungal sensitisation

  • Parasitic infections

When eosinophils are activated and break down, they release galectin-10.
If enough of this protein accumulates in thick airway mucus, it crystallises into visible crystals.

So the crystals are made from your immune cells, not from Aspergillus.

🫁 Why Do They Appear in ABPA?

In ABPA:

  1. The immune system overreacts to Aspergillus fumigatus.

  2. This triggers a strong allergic (Type 2) immune response.

  3. Large numbers of eosinophils move into the airways.

  4. Eosinophils break down and release galectin-10.

  5. The protein crystallises inside mucus plugs.

The crystals are therefore a footprint of intense allergic inflammation, not fungal invasion.

🌡 Is Most ABPA Eosinophilic?

Yes — almost all classical ABPA is eosinophilic.

ABPA is fundamentally a Type 2 allergic condition, driven by immune pathways involving:

  • IL-4

  • IL-5

  • IL-13

  • IgE

  • Eosinophils

IL-5 in particular stimulates eosinophil production and survival.
Because of this, eosinophils are central to the disease process.

Historically, raised blood eosinophils have been part of diagnostic criteria.

However:

  • Eosinophil counts can fluctuate

  • Steroids can suppress blood levels

  • Eosinophils may still be present in airway mucus even if blood counts appear normal

So ABPA is biologically eosinophilic — even if a single blood test does not show a high count.

True non-eosinophilic ABPA would be unusual and would prompt clinicians to reconsider the diagnosis.

❓ Are Crystals Caused by Aspergillus Infection?

No.

They are caused by the immune reaction to Aspergillus — not by the fungus itself.

They can also be seen in:

  • Severe eosinophilic asthma

  • Parasitic infections

  • Other allergic lung conditions

They reflect eosinophil activity, not fungal growth.

🧠 Why Don’t All People with Asthma Develop These Crystals?

Asthma is not one single disease. It has different inflammatory patterns.

Type 2 (Eosinophilic) Asthma

This involves high eosinophils and allergic pathways.

Common in:

  • Allergic asthma

  • ABPA

  • Severe eosinophilic asthma

These patients can develop Charcot–Leyden crystals.

Non–Type 2 (Non-Eosinophilic) Asthma

This includes:

Neutrophilic asthma

Driven by neutrophils rather than eosinophils.

Paucigranulocytic asthma

Very few inflammatory cells present.

In these forms:

  • Eosinophils are low

  • Galectin-10 is not released in large amounts

  • Crystals are unlikely to form

🧱 Do Charcot–Leyden Crystals Make Mucus Plugs Worse?

Possibly.

Research suggests they may:

  • Increase mucus thickness

  • Contribute mechanically to airway blockage

  • Stimulate further inflammation

For many years they were thought to be harmless debris.
Modern studies suggest they may actively amplify inflammation when present in large amounts.

🎯 Do They Have a Purpose?

Eosinophils evolved mainly to help fight parasitic infections.

Galectin-10 probably has immune signalling roles inside cells.

However, when large amounts are released into thick airway mucus, crystallisation appears to be a by-product of excessive immune activity rather than a useful defence.

In ABPA and allergic asthma, they are more likely part of the problem than part of the solution.

💧 Can Their Formation Be Reduced?

Hydration alone does not stop them forming.

Drinking fluids helps:

  • Keep mucus less sticky

  • Support airway clearance

But it does not prevent eosinophils releasing galectin-10.

What reduces crystal formation?

Reducing eosinophilic inflammation:

  • Corticosteroids

  • Anti-IL-5 biologics

  • Anti-IL-4/IL-13 biologics

When eosinophil numbers fall:

→ Less galectin-10 is released
→ Fewer crystals form

Antifungal treatment in ABPA may indirectly help by reducing allergic stimulation, but the main driver is the immune response.

📊 Do They Change Treatment?

Not directly.

Doctors base treatment on:

  • Symptoms

  • Blood eosinophils

  • Total IgE

  • Imaging

  • Lung function

  • Exacerbation history

Crystals support the diagnosis of eosinophilic inflammation but do not determine treatment alone.

🔎 What Do They Tell Us?

Charcot–Leyden crystals tell us:

  • The airway inflammation is eosinophilic.

  • The immune response is strongly allergic.

  • Mucus plugging risk may be higher.

They are a marker of immune overreaction, not infection severity.

🧠 Key Points to Remember

  • They are made from proteins released by eosinophils.

  • They are not Aspergillus.

  • They do not mean invasive fungal infection.

  • Most classical ABPA is eosinophilic.

  • They are unlikely in non-eosinophilic asthma.

  • Reducing eosinophils reduces their formation.

  • Hydration helps clearance but does not prevent formation.

In simple terms:

Charcot–Leyden crystals are microscopic signs that the immune system is working too hard in the airways.

by GAtherton

Invitation: Patient & Carer Discussion on Living with ABPA. New type of treatment.

🕙 10:00am, Thursday 12th

Get details on how to join us by clicking on the link below and choosing Thursday 12th Patients Support Meeting - you will be sent a link to the meeting via email.

https://outlook.office.com/book/[email protected]/

We are inviting people living with Allergic Bronchopulmonary Aspergillosis (ABPA), and those who care for them, to take part in an open, informal online discussion with argenx, a research-focused biotechnology company.

argenx would like to listen directly to patients and carers to better understand what day-to-day life with ABPA is really like. There is no need to prepare anything in advance — you are welcome simply to listen, or to share as much or as little as you feel comfortable.

They are particularly interested in hearing about:

  • Patients’ and carers’ journeys living with ABPA

  • Which symptoms are most burdensome in everyday life (for example breathlessness, cough, fatigue, thick mucus or mucus plugs)

  • Where current treatments fall short from a patient or carer perspective

  • What would make patients or carers feel motivated or reassured about taking part in a future clinical trial of a new ABPA therapy

The purpose of this conversation is to help researchers design future studies that reflect what matters most to patients, including which outcomes are meaningful and how trials can be made more patient-friendly.

📅 Date: Thursday 12th
🕙 Time: 10:00am
💬 Format: Open, informal discussion
📝 Preparation: None required

If you are living with ABPA, or care for someone who is, and would be interested in attending, please let us know.

A short explainer: what is ARGX-118?

argenx is developing an investigational (research-stage) treatment called ARGX-118. It is not yet a licensed medicine and is not currently available outside of research studies.

Case study

In ABPA, many people experience very thick, sticky mucus and mucus plugs that block airways and contribute to breathlessness, cough, and flare-ups. Research has shown that this mucus can sometimes contain microscopic crystals formed from proteins released by certain white blood cells involved in allergic inflammation. These crystals can make mucus denser and harder to clear.

ARGX-118 is designed to target and break down these crystals, with the aim of making mucus less thick and easier to clear from the lungs. This is a different approach from current treatments, which mainly focus on suppressing inflammation (such as steroids or biologics) or reducing fungal burden (antifungal medicines).

Because ARGX-118 is still in early development, we do not yet know how effective it will be, who might benefit most, or how it would fit alongside existing treatments. That is exactly why argenx wants to hear from patients and carers now — to understand real-world symptoms, treatment gaps, and what would genuinely matter if a future clinical trial were developed.

👉 Attending this meeting does not commit you to any trial and will not affect your care. It is simply an opportunity to share experiences and help shape future research, if you wish.

by GAtherton

Airways mucus and aspergillosis

A clear, patient-friendly explainer

People living with aspergillosis often say that mucus is one of the hardest symptoms to manage — thick sputum, coughing fits, plugs that feel “stuck”, and flare-ups that seem to come out of nowhere. This explainer brings everything together in one place: what mucus is for, why aspergillosis causes so much of it, why it becomes abnormal, and what current and future treatments aim to do.

1. What is airway mucus and why do we need it?

Mucus is normal, healthy, and essential. Everyone produces it all the time.

Its main roles are to:

  • Trap inhaled particles (dust, spores, bacteria, pollution)

  • Protect the airway lining from drying and irritation

  • Support the immune system

  • Clear the lungs, using tiny moving hairs (cilia) that sweep mucus upwards so it can be swallowed or coughed out
    (this clearance system is called the mucociliary escalator)

In healthy lungs:

  • Mucus is thin

  • Produced in small amounts

  • Cleared without you noticing it

2. Why aspergillosis causes excessive mucus

In aspergillosis, the lungs are under ongoing stress. Several factors combine:

Persistent immune activation

The immune system keeps reacting to Aspergillus material in the airways. Even when the fungus is controlled, inflammation can persist.

Allergic-type inflammation (especially in ABPA)

Allergic immune responses strongly stimulate mucus-producing cells, leading to:

  • Large volumes of mucus

  • Very sticky or rubbery sputum

Airway damage

Conditions commonly associated with aspergillosis (such as bronchiectasis or long-standing asthma) cause:

  • Widened or damaged airways

  • Poor mucus clearance

  • Pools of mucus that are hard to shift

Slowed clearance

Inflammation and infection impair cilia, so mucus:

  • Moves more slowly

  • Sits in the lungs longer

  • Becomes thicker and harder to clear

➡️ What starts as a protective response becomes a self-perpetuating problem.

3. Why thick mucus causes symptoms

Excess or abnormal mucus can:

  • Block airways → breathlessness and wheeze

  • Trigger coughing → especially overnight or on waking

  • Trap infection → repeated flare-ups

  • Reduce oxygen exchange

  • Increase fatigue and chest discomfort

Many patients describe it as:

“Glue-like”, “stringy”, “rubbery”, or “impossible to move”

4. Mucus plugs and crystals – why some mucus is so hard to clear

Mucus plugs

When mucus becomes very thick, it can:

  • Form plugs that partially or completely block airways

  • Show up on CT scans

  • Worsen breathlessness suddenly

Charcot–Leyden crystals

In allergic and eosinophilic airway disease (including allergic bronchopulmonary aspergillosis):

  • Breakdown products of allergic immune cells can form microscopic crystals

  • These crystals make mucus:

    • Stiffer

    • More irritating

    • Harder to clear

Their presence is a sign of ongoing allergic inflammation, not infection alone.

5. Why managing mucus really matters

Mucus is not just an inconvenience. Poor mucus control can:

  • Increase infection risk

  • Drive repeated exacerbations

  • Worsen lung damage over time

  • Reduce quality of life and sleep

  • Increase hospital admissions

For aspergillosis, mucus management is core treatment, not optional.

6. What helps now (current approaches)

A. Thin the mucus

  • Good hydration

  • Nebulised saline (normal or hypertonic)

  • Selected mucolytic medicines (used carefully)

B. Move it out

  • Regular airway clearance physiotherapy

  • Breathing techniques (e.g. active cycle breathing)

  • Oscillating devices (flutter, Acapella, Aerobika)

  • Gentle, regular physical activity where possible

C. Reduce inflammation

  • Inhaled corticosteroids (when appropriate)

  • Oral steroids (used cautiously)

  • Biologic therapies for selected allergic or eosinophilic disease

  • Antifungal treatment when fungal burden is contributing

D. Treat infections early

  • Bacterial infections thicken mucus further

  • Prompt treatment reduces long-term damage

7. What research is doing differently (emerging therapies)

Research is moving beyond simply “loosening mucus”.

1. Reducing mucus production at source

Scientists are developing drugs that aim to:

  • Switch off excessive mucus secretion

  • Preserve normal protective mucus

This targets the mucus-producing cells directly.

2. Blocking the signals that drive over-production

Inflammation sends chemical signals telling airways to make more mucus. New treatments aim to:

  • Calm allergic and immune pathways

  • Prevent expansion of mucus-producing cells

Some current biologic therapies already reduce mucus indirectly; future drugs will be more precise.

3. Changing mucus structure

Instead of thinning everything, researchers are studying ways to:

  • Loosen the internal “mesh” of mucus

  • Prevent dense plugs from forming

  • Restore normal movement by cilia

4. Targeting mucus crystals

In allergic aspergillosis, research is exploring how to:

  • Reduce crystal formation

  • Calm the specific immune responses that create them

5. New inhaled and physical approaches

Early trials are testing:

  • Inhaled therapies designed to mobilise secretions

  • Treatments that improve airflow behind mucus plugs

6. Precision medicine

Future mucus treatments are likely to be:

  • Personalised

  • Based on inflammation type, fungal involvement, airway damage, and immune markers

Two people with aspergillosis may have very different mucus drivers — and need different solutions.

8. What this means for patients today

  • There is no single “anti-mucus cure” yet

  • Promising therapies are in research and early trials

  • Safety and long-term effects must be proven first

For now:

  • Regular airway clearance remains essential

  • Treating inflammation and infection promptly is crucial

  • Understanding why your mucus behaves as it does helps guide treatment

Key messages to remember

  • Mucus is normally protective

  • Aspergillosis turns a helpful system into a problem

  • Thick, sticky mucus reflects ongoing inflammation and airway damage

  • Crystals signal allergic involvement, not just infection

  • Research is moving toward preventing abnormal mucus formation, not just thinning it

by GAtherton

Hyper-IgE syndrome

A patient-friendly guide (and why it matters if you have aspergillosis)

Hyper-IgE syndrome is a rare condition of the immune system. People with it have very high levels of an antibody called Immunoglobulin E (IgE), but their immune system does not work properly at fighting certain infections.

It is not the same as having lots of allergies, even though it can look very similar at first.

What is IgE, and why does it matter?

IgE is usually involved in allergies and asthma.

In Hyper-IgE syndrome:

  • IgE levels are extremely high (often many thousands)

  • But the immune system is unbalanced

  • This makes infections—especially in the lungs and skin—harder to control

So IgE is high, but protection is weak.

How might Hyper-IgE syndrome affect everyday life?

Not everyone has the same symptoms, but common features include:

Lung and chest problems

  • Repeated chest infections (often from a young age)

  • Ongoing cough, breathlessness and mucus

  • Lung damage such as bronchiectasis

  • Lung cavities that can later become infected by moulds such as Aspergillus

Skin and infection problems

  • Long-standing eczema or very sensitive skin

  • Recurrent skin infections or boils

  • Infections that keep coming back or take a long time to clear

Other clues (in some people)

  • Frequent infections in childhood

  • Bone or joint problems

  • Dental issues (for example baby teeth not falling out on time)

Why is this important for people with aspergillosis?

For many people, Aspergillus causes allergy or irritation.

In Hyper-IgE syndrome:

  • The immune system struggles to control moulds

  • Aspergillus can behave more like a true infection, not just an allergy

  • Lung damage can happen more easily and progress faster

This means doctors may need to:

  • Monitor lungs more closely

  • Treat fungal disease earlier and for longer

  • Be cautious with repeated or long-term steroid use

Specialist centres such as the National Aspergillosis Centre are often involved when aspergillosis and immune problems overlap.

Isn’t this just severe allergy or ABPA?

Hyper-IgE syndrome can look similar to:

  • Severe allergic asthma

  • Allergic Bronchopulmonary Aspergillosis (ABPA)

The key difference is that in Hyper-IgE syndrome:

  • The immune system itself is faulty

  • High IgE is part of a wider immune problem

  • Treating allergy alone may not be enough

Some people are treated for asthma or ABPA for years before this possibility is considered.

How is Hyper-IgE syndrome treated?

There is no single cure, but good treatment can make a big difference. The aim is to prevent infections, protect the lungs, and reduce symptoms.

1. Preventing infections (most important)

Because the immune system does not fight germs normally:

  • Some people take regular low-dose antibiotics

  • Others use antibiotics early and promptly when infections start

For people with aspergillosis:

  • Antifungal medicines may be needed

  • Monitoring is usually closer and longer-term

2. Protecting the lungs

Many people develop bronchiectasis or lung damage, so care often includes:

  • Airway clearance physiotherapy

  • Saline nebulisers to help clear mucus

  • Regular sputum tests

  • Early treatment of flare-ups

The goal is to stop the cycle of:

infection → inflammation → permanent lung damage

3. Managing inflammation and allergy (carefully)

People may also have asthma-like symptoms, eczema and multiple allergies.

  • Steroids can help symptoms, but long-term or frequent use can increase infection risk

  • Doctors usually try to keep steroid doses as low as possible

Biologic treatments (such as anti-IgE medicines):

  • May help some people

  • Do not fix the immune problem

  • Are considered on an individual basis, usually in specialist centres

4. Skin care

  • Regular moisturising

  • Prompt treatment of infected eczema

  • Good skin care helps reduce infection risk

How is Hyper-IgE syndrome diagnosed?

Diagnosis usually involves:

  • A detailed review of your medical history (often including childhood infections)

  • Blood tests of immune function

  • Referral to an immunology specialist

  • Sometimes genetic testing

Does having high IgE mean I definitely have this?

No.
Hyper-IgE syndrome is rare.

But it may be worth asking about if:

  • Your IgE has always been extremely high

  • You’ve had repeated infections for many years

  • You have bronchiectasis without a clear cause

  • Aspergillosis seems unusually persistent or severe

  • Standard asthma or allergy treatments don’t fully explain your symptoms

Key message

Very high IgE does not always mean “just allergy.”
In a small number of people, it reflects a deeper immune problem that changes how aspergillosis behaves and how it should be treated.

If your illness doesn’t quite fit the usual labels, it is reasonable to ask whether an immunology review would help.

by GAtherton

Sinusitis in Patients with ABPA

When to suspect it, when to investigate, and when to refer

Why this matters

Patients with allergic bronchopulmonary aspergillosis (ABPA) are usually managed as having a lung disease. Diagnosis, monitoring, and treatment focus appropriately on the chest, immunology, and asthma control.

However, ABPA occurs within a single continuous airway, extending from the nose and sinuses to the lungs. Disease in the upper airway can coexist with, exacerbate, or complicate lower airway inflammation — yet sinus disease is not routinely assessed in ABPA care pathways.

This article outlines:

  • What is known about sinus disease in this context

  • Which symptoms should raise suspicion

  • When investigation or ENT referral should be considered

  • What GPs and non-specialists can reasonably do

The united airway: a brief reminder

The upper and lower airways share:

  • Type 2 (eosinophilic) inflammation

  • Immunoglobulin E–mediated immune responses

  • Common triggers, including allergens and fungi

Chronic rhinosinusitis is common in asthma and severe asthma, and treatment of sinus disease can improve lower airway outcomes in some patients.
ABPA sits within this same inflammatory spectrum, even though its management is lung-centred.

Sinus disease in ABPA: what is (and isn’t) known

What we know

  • Chronic rhinosinusitis is common in patients with asthma and severe asthma

  • Sinus disease may be symptomatic or relatively silent

  • ABPA guidelines do not mandate routine ENT review or sinus imaging

  • ENT involvement, therefore, varies widely between centres

What we do not know

  • Whether routine ENT assessment improves ABPA outcomes

  • Which ABPA patients benefit most from sinus intervention

  • The optimal timing for ENT referral in ABPA

As a result, clinical judgement remains central.

Symptoms that should prompt consideration of sinus disease

Sinusitis in ABPA patients does not always present with classic “blocked nose and facial pain”.
Key symptoms include:

Common but often overlooked

  • Persistent post-nasal drip

  • Foul, bitter, metallic, or “infected” taste in the mouth

  • Throat clearing, chronic cough

  • Thick or sticky mucus sensation

  • Symptoms are worse on waking or lying flat

More typical sinonasal features

  • Nasal blockage or congestion

  • Facial pressure or fullness

  • Reduced or altered sense of smell

  • Nasal crusting or discharge

Contextual clues

  • Poor durability of response to steroids or antifungals

  • Recurrent “flares” without clear chest triggers

  • Coexisting severe asthma or nasal polyps

  • Symptoms are worse in damp or mould-affected housing

A persistent foul taste in the mouth is a recognised symptom of chronic sinus disease, usually due to post-nasal drainage of inflamed secretions.

Damp homes and sinus disease

Living in damp or mould-affected environments is associated with:

  • Higher rates of chronic rhinosinusitis

  • Upper airway irritation and inflammation

  • Allergic sensitisation to fungal spores

In most cases, this results in inflammatory or allergic sinusitis, not invasive fungal infection.
Fungal involvement may act as an immune trigger, even when not labelled as “fungal sinusitis”.

Fungal sinusitis: rare vs under-recognised

It is important to distinguish between entities:

Type Frequency Key point
Invasive fungal sinusitis Rare Usually immunocompromised; dramatic presentation
Fungal ball (mycetoma) Uncommon Usually obvious on CT
Allergic fungal rhinosinusitis Likely under-recognised Requires active suspicion

Allergic fungal rhinosinusitis overlaps biologically with ABPA:

  • IgE-mediated

  • Eosinophilic inflammation

  • Thick allergic mucin

It is not routinely sought, so it may be under-diagnosed in at-risk groups.

What GPs and non-specialists can reasonably do

1. Take upper airway symptoms seriously

Especially in ABPA or severe asthma patients with:

  • Persistent post-nasal symptoms

  • Foul taste

  • Recurrent unexplained deterioration

2. Examine the nose and throat

  • Look for polyps, discharge, and crusting

  • Note mouth breathing or altered voice quality

  • Check dentition (to exclude dental causes)

3. Consider imaging when symptoms persist

  • CT sinuses (not plain X-ray) is the imaging of choice

  • Particularly appropriate if symptoms last >8–12 weeks or recur

4. Refer to ENT when:

  • Symptoms are persistent or progressive

  • CT shows significant sinus disease

  • There is a poor response to standard medical therapy

  • There is diagnostic uncertainty

Referral does not imply surgery — ENT input may be diagnostic or medical.

What this article is not saying

  • It does not suggest that all ABPA patients need an ENT referral

  • It does not claim that sinus treatment improves ABPA outcomes

  • It does not override existing guidelines

It does suggest that earlier consideration of the upper airway is reasonable in selected patients.

Key take-home points for clinicians

  • The airway functions as a single inflammatory system

  • Sinus disease may be subtle, under-reported, or atypical

  • A foul taste in the mouth is a meaningful symptom

  • Damp or mould exposure increases sinus disease risk

  • ENT referral is appropriate when symptoms persist or recur

  • Evidence gaps remain — but clinical vigilance is justified

In summary

ABPA is managed as a lung disease, but patients live with a whole airway.
Recognising when sinus disease may be contributing can help explain persistent symptoms and guide appropriate referral — without over-investigation or over-treatment.

by GAtherton