Eosinophilic Pneumonia

Eosinophilic pneumonias are a group of disorders characterised by pulmonary infiltrates with eosinophilia in blood, lung tissue or bronchoalveolar lavage. Main forms are acute and chronic eosinophilic pneumonia, with secondary causes of pulmonary eosinophilia.

Differential causes of pulmonary eosinophilia

• Idiopathic: acute eosinophilic pneumonia, chronic eosinophilic pneumonia, idiopathic hypereosinophilic syndrome.
• Drugs and toxins: nitrofurantoin, NSAIDs, antibiotics (daptomycin, minocycline), antiepileptics, sulfasalazine, L tryptophan, cocaine.
• Parasitic (Loeffler syndrome, tropical pulmonary eosinophilia from filariasis, Ascaris, Strongyloides, Toxocara, hookworm, schistosomiasis).
• Allergic bronchopulmonary aspergillosis and fungal infection.
• Eosinophilic granulomatosis with polyangiitis, Churg Strauss.
• Malignancy (lymphoma), sarcoidosis, IgG4 related disease.
• Diagnosis requires BAL eosinophils over 25% (greater than 40% suggests CEP/AEP) or lung biopsy with eosinophilic infiltrate, peripheral eosinophilia (CEP) over 500 cells/µL in most.

• Cough, dyspnoea, fever, wheeze, night sweats, weight loss, chest pain.
• Skin rash, sinusitis, neuropathy, cardiac involvement suggest EGPA or hypereosinophilic syndrome.
• Travel and exposure history; medication review.

• Full blood count with differential and film, IgE, ESR, CRP.
• Stool microscopy for ova and parasites, Strongyloides and Toxocara serology, filarial antibodies.
• Aspergillus specific IgE and precipitins, ANCA (MPO), troponin, echocardiography.
• Chest radiograph and HRCT; bronchoalveolar lavage; biopsy rarely.
• Spirometry; sinus imaging.
• Exclude infection (tuberculosis, fungus) before steroids.

• Remove the offending drug or exposure.
• Treat parasites: ivermectin 200 micrograms/kg for Strongyloides (2 days) before steroids in at risk patients; diethylcarbamazine 6 mg/kg/day for 12 to 21 days for tropical pulmonary eosinophilia; albendazole 400 mg for Ascaris/Toxocara.
• Idiopathic eosinophilic pneumonias: prednisolone as in the specific articles.
• EGPA or hypereosinophilic syndrome: prednisolone with immunosuppressants; mepolizumab 300 mg SC every 4 weeks for EGPA, 100 mg for asthma.
• ABPA: see bronchiectasis.
• Refractory: benralizumab 30 mg SC, mepolizumab, reslizumab; imatinib 100 to 400 mg for FIP1L1 PDGFRA positive disease.
• Follow up with eosinophil counts and imaging.