Can chronic pulmonary aspergillosis (CPA) cause high peripheral eosinophilia?

Can Chronic Pulmonary Aspergillosis Cause High Peripheral Eosinophilia?

No, chronic pulmonary aspergillosis (CPA) does not typically cause high peripheral eosinophilia. This finding should prompt consideration of allergic bronchopulmonary aspergillosis (ABPA) rather than CPA, as these represent distinct disease entities with different immunologic profiles.

Key Distinguishing Features

CPA Does NOT Present with Eosinophilia

• CPA is characterized by chronic cavitary disease, fungal balls, and progressive lung destruction over at least 3 months in patients with underlying structural lung disease 1
• The immunologic profile shows elevated Aspergillus-specific IgG antibodies (positive in >90% of cases), but peripheral eosinophilia is not a feature 1, 2
• CPA occurs in non-immunocompromised patients and represents a chronic infection rather than an allergic response 3

ABPA DOES Present with Eosinophilia

• ABPA is defined by peripheral blood eosinophilia as a core diagnostic criterion 1
• ABPA results from immune-mediated inflammation in response to inhaled Aspergillus fumigatus antigen, causing pulmonary infiltrates, mucus plugging, and marked eosinophilia 1, 4, 5
• Essential diagnostic criteria for ABPA include: asthma or cystic fibrosis, immediate cutaneous reactivity to Aspergillus, elevated total serum IgE (>417 IU/L), elevated Aspergillus-specific IgG and IgE, and peripheral blood eosinophilia 1, 4
• The eosinophilia in ABPA is driven by increased CD4+ Th2 lymphocytes and IL-5, with Aspergillus serving as a growth factor for eosinophils 4, 5

Critical Clinical Pitfall

The presence of high peripheral eosinophilia in a patient with pulmonary aspergillosis strongly suggests ABPA rather than CPA. This distinction is crucial because:

• Treatment differs fundamentally: ABPA requires systemic corticosteroids as first-line therapy with antifungals as adjunctive treatment 1, 4
• CPA requires prolonged antifungal therapy (at least 6 months) without routine corticosteroid use 1, 6
• Using corticosteroids in CPA patients can worsen infection and potentially lead to invasive aspergillosis 6

Diagnostic Algorithm When Eosinophilia is Present

When encountering a patient with suspected pulmonary aspergillosis and peripheral eosinophilia:

1. Check for asthma or cystic fibrosis history - ABPA occurs almost exclusively in these populations 1, 4

2. Measure total serum IgE - Levels >417 IU/L support ABPA; CPA does not cause IgE elevation 1

3. Review imaging for pattern:

   • Central bronchiectasis, mucus plugging, and infiltrates suggest ABPA 1
   • Cavities with fungal balls and pleural thickening suggest CPA 1

4. Assess Aspergillus-specific antibodies:

   • Both IgE and IgG elevated = ABPA 1
   • Only IgG elevated without eosinophilia = CPA 1, 2

Other Differential Diagnoses with Eosinophilia

When pulmonary disease and eosinophilia coexist, consider:

• Chronic eosinophilic pneumonia - peripheral infiltrates, no Aspergillus sensitization 4
• Churg-Strauss syndrome (EGPA) - systemic vasculitis features 4
• Tropical pulmonary eosinophilia - filarial infection, may coexist with ABPA 7
• Parasitic infections - travel history relevant 4
• Drug-induced pulmonary infiltrates - medication review essential 4

The presence of high peripheral eosinophilia fundamentally changes the diagnostic approach and should redirect evaluation toward ABPA or other eosinophilic lung diseases rather than CPA 1, 4.