A Case of Chronic Neutrophilic Leukemia Successfully Treated with Pegylated Interferon Alpha-2a

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm (MPN) that represents a diagnostic dilemma for both clinicians and pathologists. Because this disease entity is very rare, and because its diagnosis is by exclusion, it is important for clinical hematologists and hematopathologists to be familiar with CNL when approaching patients with MPNs and persistent neutrophilia. A woman in her 40s who was incidentally found to have leukocytosis was referred to the hematology service at the National Center for Cancer Care and Research for evaluation. Complete blood count revealed hyperleukocytosis with predominant neutrophilia. Peripheral blood and flow cytometry did not show any evidence of lymphoproliferative disorder or myeloblasts. Bone marrow aspirate and biopsy revealed a hypercellular marrow with myeloid hyperplasia. Cytogenetics revealed normal karyotype. Tests for both Janus kinase mutation JAK2 V617F and rearrangement of the genes BCR-ABL1, platelet-derived growth factor receptor-α (PDGFRα), PDGFRβ, and fibroblast growth factor receptor-1 (FGFR1) were negative. Thereafter, the diagnosis of CNL was reached. She was treated with pegylated interferon alpha-2a, with very good hematological response. To the best of our knowledge, this is the first case of CNL reported among the Arab population.