Monoclonal eosinophilia reflects the expression of chronic eosinophilic leukemia. Marrow contains principally eosinophilic myelocytes and mature eosinophils, some with hypersegmented nuclei (more than two segments).
— Onset occurs with some or all of the following: anorexia, weight loss, fatigue, nausea, abdominal pain, diarrhea, nonproductive cough, pruritic rash, fever, night sweats, and venous thrombosis.
— Skin signs include urticaria, papules, and pruritus.
— Cardiac involvement may be marked by endomyocardial fibrosis, restrictive cardiomyopathy, mitral or tricuspid valve incompetence, ventricular failure, conduction defects, and arrhythmias.
— Neurologic findings include neuropathies; these may lead to encephalopathy, polyneuropathy, or stroke.
— Hepatosplenomegaly, interstitial pulmonary infiltrates, and pleural effusions can occur.
— Nervous system dysfunction may be profound, including confusion, delirium, dementia, and coma.
— Hematologic manifestations. All patients have leukocytosis with a striking eosinophilia, usually eosinophil counts greater than 1.5 × 109/L, and counts of 50.0 × 109/L or more are found in more than half the patients; eosinophilia may be progressive; anemia occurs in most patients; and thrombocytopenia is seen occasionally.
— Cytogenetic abnormalities may be found in the leukemic eosinophilic cells in a proportion of patients. One of several translocations involving chromosome 5 may occur. Of particular importance is the occurrence of the FILIPI-PDGFR-α fusion gene because, if present, the patient will usually respond to tyrosine kinase inhibitor drugs, such as imatinib mesylate.
— Elevated serum tryptase is common (suggesting unapparent mast cell involvement).
— The disease is sometimes indolent but more often progressive and fatal.
— Signs and symptoms may remit and relapse, but organ damage is usually progressive.
— Episodes of venous thrombosis may complicate the course.
— Therapy. In patients unresponsive to tyrosine kinase inhibitors, hydroxyurea and glucocorticoids may be of benefit in decreasing the eosinophil count and the risk of tissue injury. Other therapies include etoposide, interferon-α, cladribine, and leukapheresis. Allogeneic hematopoietic cell transplantation has been used in some patients.
— Surgical replacement of severely damaged heart valves has been successful.