Eosinophilia

Eosinophilia is defined as a peripheral eosinophil count is greater than 0.44 x 10⁹/l. In many cases the cause is clear, e.g. atopic disease. However the differential diagnosis includes many more serious diseases, including malignancy.

• In the UK, eosinophilia is most often due to allergic conditions.
• Worldwide, helminth infections are the most common cause of eosinophilia.

• Travel history to assess whether a patient has travelled to an area that is endemic for certain infections, including helminthic infections.
• Medication and diet history to evaluate for allergic reactions associated with eosinophilia.
• History of symptoms associated with possible underlying causes (see below).
• A history suggestive of adrenal insufficiency, including the use and tapering of corticosteroid medications, can provide a clue that the observed eosinophilia is associated with adrenal insufficiency.
• A complete physical examination is required because diseases associated with eosinophilia can involve any part of the body.

• Allergic/atopic diseases: asthma, urticaria, eczema, allergic rhinitis, drug hypersensitivity, angioneurotic oedema
• Connective tissue diseases: Churg-Strauss syndrome, rheumatoid arthritis, eosinophilic fasciitis, polyarteritis nodosa
• Infections:
  • Convalescence from any infection
  • Schistosomiasis, echinococciasis, coccidioidomycosis
  • Human T-cell lymphotropic virus I (HTLV-I)
• Hypereosinophilic syndrome
• Neoplasia:
  • Lymphoma (e.g. Hodgkin lymphoma, non-Hodgkin lymphoma)
  • Leukaemia: chronic myeloid leukaemia, adult T-cell leukaemia/lymphoma (ATLL), eosinophilic leukaemia (very rare)
  • Gastric cancer or lung carcinoma (i.e. paraneoplastic eosinophilia)
• Endocrine: Addison's disease
• Skin disease - pemphigus, dermatitis herpetiformis, erythema multiforme
• Loffler's syndrome
• Loffler's endocarditis (restrictive cardiomyopathy with eosinophilia)
• Eosinophilia myalgia syndrome
• Irradiation
• Post-splenectomy
• Cholesterol emboli
• Drugs, e.g. penicillins, streptomycin

• Full blood count, including differential white cell count.
• Lumbar puncture: CSF eosinophilia due to worm infections (e.g. Angiostrongylus cantonensis), drug reactions, and coccidioidomycosis fungal meningitis.
• CT scans of the lungs, abdomen, pelvis, and brain evaluate for focal defects due to diverse causes of eosinophilia, e.g.:
  • Worm infections of the liver (e.g. Fasciola hepatica) can cause focal hepatic lesions.
  • Coccidioidomycosis fungal infection can cause focal lesions in the lung, which are visible on a chest x-ray or CT scan.
  • Hodgkin or non-Hodgkin lymphoma can cause lymphadenopathy in the abdomen, which can be seen on a CT scan.
• Echocardiogram to assess for thrombi (e.g. mural, endocardial) due to Hypereosinophilic syndrome
• Cystoscopy: all patients with blood eosinophilia and haematuria and who have been in Africa should have their urine examined for the eggs of Schistosoma haematobium. Cystoscopy may be required to confirm the diagnosis.