A rare cause of persistent leukocytosis with massive splenomegaly: Myeloid neoplasm with BCR-PDGFRA rearrangement-Case report and literature review.

RATIONALE: Persistent leukocytosis with megalosplenia is a common manifestation among patients with myeloproliferative neoplasm (MPN), especially for chronic myeloid leukemia (CML) patients. Here, we report a rare case of myeloid neoplasm with BCR-PDGFRA rearrangement characterized by obvious elevation of leukocyte count and megalosplenia. PATIENT CONCERNS: A 32-year-old man presented with persistent leukocytosis and megalosplenia. DIAGNOSIS: This patient was characterized by increased leukocyte count and megalosplenia, and was clinically diagnosed as CML. However, the BCR/ABL fusion gene of the patient was negative, which did not support CML. Moreover, the results of the karyotype showed 46, XY, t(4;22)(q12;q11) and RT-PCR + Sanger detection showed positive PDGFA/BCR. Accordingly, the diagnosis of myeloid neoplasm with BCR-PDGFA rearrangement was confirmed. INTERVENTIONS: This patient was initially received imatinib (400 mg) orally once a day, and the dosage was adjusted to 100 mg owing to suffering from grade IV bone marrow suppression. OUTCOMES: Hematological remission was achieved after 2 weeks, the best treatment response was achieved after 3 months, and the main molecular biological response was achieved after 12 months. LESSON: This case suggests that rare PDGFA fusion genes screening for patients comorbid with leukocytosis and megalosplenia is necessary to avoid misdiagnosis. Unlike other rearrangements of PDGFRA, the clinical manifestations of BCR-PDGFRA rearrangement are resembling CML without eosinophilia increase.