Eosinophilia

Eosinophilia is a hematologic condition characterized by an elevated concentration of eosinophils, a specialized subset of white blood cells integral to immune responses against parasitic infections and allergic reactions. While eosinophils normally constitute less than 5% of circulating leukocytes, their excessive accumulation can trigger tissue inflammation and organ damage.

Definition and Classification

Eosinophilia is defined as an absolute eosinophil count (AEC) exceeding 500 cells per microliter (500/µL) of blood. Severity stratification includes mild (500–1,500/µL), moderate (1,500–5,000/µL), and severe (>5,000/µL). Hypereosinophilia denotes persistent counts >1,500/µL for over six months, often associated with hypereosinophilic syndrome (HES), a disorder causing multi-organ involvement.

Etiology and Pathophysiology

Primary causes encompass allergic disorders (asthma, atopic dermatitis, hay fever), parasitic infestations (helminths, filariasis), drug hypersensitivity reactions, autoimmune conditions, and malignancies (Hodgkin lymphoma, leukemia, myeloproliferative neoplasms). Eosinophils release cytotoxic granule proteins (e.g., major basic protein, eosinophil cationic protein) that combat pathogens but may damage host tissues when overproduced.ncbi.nlm.nih+3

Clinical Manifestations and Management

Mild cases are often asymptomatic. Diagnosis involves complete blood count (CBC), differential, and evaluation for underlying etiology. Treatment targets causative conditions, corticosteroids for inflammation, and targeted therapies (e.g., anti-IL-5 agents) for refractory cases.