Synopsis
Interpret persistent eosinophilia and basophilia by absolute count, tempo and organ involvement, distinguish reactive from clonal disease and escalate eosinophilic organ injury or a myeloid-neoplasm phenotype promptly.
- Use absolute eosinophil and basophil counts, not percentages, and confirm persistence and trajectory. A high percentage during neutropenia may represent a normal absolute population.
- Eosinophilia is most often reactive to allergy, asthma, medicines or infection, but severity, duration, constitutional symptoms, splenomegaly and organ injury determine the need for clonal testing.
- Take a precise medicine timeline including antibiotics, anticonvulsants, allopurinol, supplements and recent stopped drugs; systemic drug hypersensitivity can continue after the culprit is withdrawn.
Key red flags
Fever, widespread rash, facial oedema, lymphadenopathy, liver or kidney injury after a medicine suggests DRESS or another systemic hypersensitivity syndrome.
Investigation priorities
Confirm persistence, verify basophils and identify reactive or clonal accompanying changes.
Management branches
Eosinophilia accompanies cardiac, respiratory, neurological, thrombotic or rapidly progressive systemic disease.
- Use ABCDE and obtain urgent FBC, film, renal, liver, coagulation, troponin, ECG and phenotype-led imaging, involving haematology plus the threatened-organ specialty immediately.
- Take parasite, molecular, flow and tissue samples before treatment where feasible; preferred initial anti-inflammatory treatment is specialist-directed systemic corticosteroid when eosinophilic organ injury is strongly supported.
Key medicines
Prednisolone for organ-threatening eosinophilic diseaseA BSH emergency regimen is 1 mg/kg by mouth once daily under specialist supervision after urgent diagnostic samples when this causes no harmful delay; use an intravenous corticosteroid only through the acute organ-support protocol.