Aspergillosis, immunity, and risk

Primary immune deficiencies and immune modifiers explained

A single, comprehensive explainer for expert patients, carers, and non-specialists

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Why this article exists

Aspergillus is a mould that everyone breathes in every day. Most people clear it without difficulty.
A small number of people develop aspergillosis because the balance between the fungus, the lungs, and the immune system is disturbed.

This article explains:

• Rare primary (inherited) immune deficiencies that are clearly linked to aspergillosis

• Common immune “modifier” factors that can increase risk or severity but do not cause disease on their own

• How these factors stack together in real life

Key reassurance up front

• There are 500+ recognised primary immune deficiencies

• Only ~20–30 are clearly linked to aspergillosis

• Most people with aspergillosis do not have any inherited immune disorder

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The unifying concept: three immune pathways to aspergillosis

Almost all immune–aspergillus relationships fall into three mechanisms. Understanding these matters more than memorising names.

1. Reduced ability to kill the fungus

Some immune cells fail to destroy Aspergillus spores effectively.
→ Risk of invasive aspergillosis, sometimes severe or life-threatening.

2. Lung damage over time

Repeated infections or inflammation damage airways or leave cavities.
→ Risk of chronic pulmonary aspergillosis (CPA) or aspergillomas.

3. Excessive allergic inflammation

The immune system over-reacts to Aspergillus rather than failing to fight it.
→ Allergic bronchopulmonary aspergillosis (ABPA) and severe fungal-sensitised asthma.

Many conditions overlap more than one pathway.

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Section 1: Primary (inherited) immune deficiencies clearly linked to aspergillosis

Rare, high-impact, and sometimes life-changing when present

These are the conditions clinicians usually mean when they talk about “immune causes of aspergillus disease”.

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A. Phagocyte defects

Strongest association with invasive aspergillosis

1. Chronic granulomatous disease (CGD)

2. Autosomal recessive forms of CGD

3. Severe congenital neutropenia

4. Cyclic neutropenia

5. Leukocyte adhesion deficiency type I

Typical pattern

• Aspergillosis at a young age

• Invasive lung disease ± spread beyond lungs

• Often no other obvious risk factors

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B. Hyper-IgE and severe allergy syndromes

Allergic, chronic, and cavity-associated disease

6. STAT3 hyper-IgE syndrome

7. DOCK8 deficiency

8. PGM3 deficiency

9. ZNF341 deficiency

10. IL6ST deficiency

Typical pattern

• Severe asthma and allergy

• Thick mucus, recurrent infections

• ABPA, later CPA or aspergillomas

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C. Combined immunodeficiencies

Immune coordination problems

11. Severe combined immunodeficiency (milder or surviving forms)

12. Omenn syndrome

13. ZAP-70 deficiency

14. Major histocompatibility complex class II deficiency

15. CD40 ligand deficiency (hyper-IgM syndrome)

Typical pattern

• Broad infection susceptibility

• Aspergillosis can behave aggressively

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D. Defects of fungal recognition and innate signalling

Often dramatic or unexpected presentations

16. CARD9 deficiency

17. Dectin-1 (CLEC7A) complete deficiency

18. MALT1 deficiency

Typical pattern

• Severe or unusual aspergillosis

• Lung, brain, or deep tissue involvement

• Sometimes first presents in adulthood

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E. Immune dysregulation syndromes

Mixed infection, inflammation, and autoimmunity

19. CTLA-4 haploinsufficiency

20. LRBA deficiency

21. STAT1 gain-of-function mutations

22. IPEX syndrome (FOXP3 deficiency)

Typical pattern

• Inflammatory lung disease

• Chronic or invasive aspergillosis emerging over time

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F. Antibody deficiencies (indirect risk via lung damage)

23. Common variable immunodeficiency

24. X-linked agammaglobulinaemia

25. Activated PI3K-delta syndrome

Important nuance
Antibodies do not normally kill Aspergillus.
Risk arises after years of lung damage, not early in life.

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Section 2: Immune modifier-types that can amplify risk

Common, low-penetrance, and often invisible on routine testing

These are not immune deficiencies, but they can influence who struggles, how severely, and why disease persists.

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Mannose-binding lectin (MBL) deficiency

• Common (≈5–10% of population)

• Affects fungal recognition and complement activation

• Usually mild on its own

• Becomes relevant with lung disease, steroids, or other immune issues

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Partial fungal-recognition receptor variants

• Heterozygous dectin-1 variants

• Toll-like receptor polymorphisms (for example TLR2, TLR4)

Effect

• Slower fungal recognition

• Increased colonisation or allergic response

• Act as risk amplifiers, not causes

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Cytokine balance variants

Small genetic differences affecting immune “signal strength”, including:

• Interleukin-6

• Interleukin-10

• Tumour necrosis factor-alpha

These modify:

• Inflammation intensity

• Tissue damage vs clearance balance

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Allergy-biased (Th2-skewed) immunity

Not a disease, but a recognised immune tendency.

Features:

• Asthma

• Eczema

• Nasal polyps

• High immunoglobulin E levels

• Eosinophilia

Strongly associated with:

• Fungal sensitisation

• ABPA

• Difficult-to-control asthma

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Impaired mucociliary clearance

A functional immune–mechanical issue.

Seen in:

• Severe asthma

• Bronchiectasis

• Chronic sinus disease

Effect:

• Aspergillus spores are not physically cleared

• Prolonged immune exposure

• Increased colonisation and allergy

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Age-related immune change (immunosenescence)

• Normal reduction in immune speed and coordination with age

• Particularly relevant to chronic pulmonary aspergillosis

Not a disease, but an important modifier of outcome.

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Airway epithelial vulnerability

Subtle weaknesses in:

• Airway lining integrity

• Antimicrobial peptide production

• Local immune signalling

Can increase:

• Fungal adherence

• Chronic colonisation

• Allergic sensitisation

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Section 3: Risk stacking – how this works in real life

Aspergillosis rarely results from one single factor.

Instead, several modest risks align:

• Mild MBL deficiency

• Severe asthma

• Corticosteroid exposure

• Bronchiectasis

• Age-related immune change

→ Together, they create real disease risk, even though none alone would.

This explains why:

• Two people with similar scans can behave very differently

• One patient relapses while another stabilises

• “Why me?” often has no single answer

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Section 4: When clinicians investigate immune causes

Testing is targeted, not routine. It is usually considered when there is:

• Aspergillosis at a young age

• Invasive or unusually severe disease

• Disease without classic risk factors

• Recurrent infections plus severe asthma or allergy

• A family history of unusual infections

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Section 5: Why identifying (or excluding) immune factors helps

Understanding immune contribution can:

• Explain disease pattern and behaviour

• Guide antifungal choice and duration

• Inform long-term prevention strategies

• Reduce future lung damage

• Reassure patients when no immune defect is found

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Key take-home messages

• Aspergillus exposure is universal; immune causes are rare

• Only ~20–30 inherited immune deficiencies are clearly linked to aspergillosis

• Modifier-type immune factors are common and usually harmless alone

• Aspergillosis often reflects risk stacking, not a single diagnosis

• Understanding patterns matters more than labels

• Specialist care improves precision and outcomes

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