[Rapidly progressive, refractory eosinophilia with a 250,000/microliter eosinophil count]

Area of Science:

• Hematology
• Oncology
• Pulmonology

Background:

• A 31-year-old male with a brain tumor on long-term corticosteroid therapy developed dyspnea and massive pleural effusion.
• Initial eosinophil counts ranged from 100 to 1,000/microliter, escalating significantly upon re-admission.

Observation:

• Peripheral blood revealed a dramatic increase in eosinophils to 48,000/microliter, with hypersegmented morphology and cytoplasmic vacuoles.
• Bone marrow showed 55% eosinophils, normal karyotype, and absence of Wilms' tumor gene.
• Elevated serum vitamin B12 and soluble IL-2 receptor, with low eosinophilopoietic cytokines (IL-3, IL-5, GM-CSF).

Findings:

• The patient experienced a rapid rise in eosinophil count, reaching 253,000/microliter despite treatments including hydroxyurea, vincristine, cytarabine, and daunorubicin.
• Monoclonal proliferation of eosinophils was not demonstrated, making the diagnosis of eosinophilic leukemia uncertain.
• This case represents the highest reported peripheral blood eosinophil count in medical literature.

Implications:

• This case underscores the potential for extreme eosinophilia in patients with brain tumors and prolonged corticosteroid use.
• The lack of response to chemotherapy and the fatal outcome highlight the aggressive nature and poor prognosis of such cases.
• Further research is needed to elucidate the mechanisms driving such profound eosinophilia and to develop effective therapeutic strategies.