Urgent considerations
See Differentials for more details
Cardiac damage
Eosinophilic cardiac damage is likely to develop from persistent eosinophilia, especially if eosinophil degranulation is prominent. The presence of cardiac failure, or of clinical or imaging signs of cardiac valve damage, mural thrombus or (occasionally) pericarditis, or thromboembolic phenomena in a patient with a high eosinophil count, mandates urgent investigation. Treatment with corticosteroids may be needed as an interim measure.
Extremely high eosinophil count (>100,000/microliter)
Investigation to determine the cause is urgent, unless it is apparent from the history and physical exam (e.g., an adverse drug reaction). High counts make subsequent tissue damage (e.g., cardiac) more likely. Treatment with intravenous corticosteroids may be needed as an interim measure.
Suspected malignancy
Malignant causes of eosinophilia are usually hematologic in origin and include leukemia (e.g., eosinophilic leukemia, chronic myeloid leukemia), Hodgkin lymphoma, and non-Hodgkin lymphoma. These can all cause a marked eosinophilia, which in the case of the lymphomas is reactive. Investigation is therefore urgent, and referral to a hematologist is a priority. The presence of lymphadenopathy or hepatosplenomegaly (either clinically or on imaging) may provide a clue to these diagnoses. Examination of the blood film for blast cells or lymphoma cells is also important.
Drug reactions
Drug reaction with eosinophilia and systemic symptoms (DRESS) (also called drug hypersensitivity syndrome) can include drug-induced rash, fever, facial edema, lymphadenopathy, and eosinophilia, as well as hepatitis, myocarditis, pneumonitis, and interstitial nephritis. Skin involvement is common and may include erythema, urticaria, papules, pustules, and exfoliative dermatitis.[9] Hematological findings include lymphocytosis, lymphopenia, atypical lymphocytes, and thrombocytopenia.
Mortality can reach 10%, usually from hepatic failure, so prompt recognition, cessation of the causative agent, and corticosteroid therapy is indicated.[9][10] See Common cutaneous drug reactions (treatment algorithm).
In excess of 40 causative drugs have been identified in literature reviews, with antibiotic and anticonvulsant drug classes most commonly implicated.[9][10] Consensus criteria to assist in the diagnosis of DRESS and to grade its severity have been developed.[11]
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