Myeloid tumors accompanying systemic mastocytosis, basophilia, and abnormal platelet-derived growth factor receptor β A case report

Introduction: Myeloid neoplasms with platelet-derived growth factor receptor beta (PDGFRB) rearrangement usually present with eosinophilia in the peripheral blood and bone marrow. Here we report a case of systemic mastocytosis related myeloid neoplasms with basophilia and PRKG2-PDGFRB fusion gene. Patient's concerns: A 53-year-old male patient felt fatigue with thrombocythemia and normal hemoglobin over 2years. Considering the possibility of primary thrombocytosis, the patient was treated with hydroxyurea and interferon. Then the therapy was stopped due to adverse events and worsen condition. Diagnosis: Acute myelogenous leukemia (AML) diagnosis was confirmed by bone marrow morphology and flow cytometry. PDGFRB rearrangement was detected by fluorescence in situ hybridization (FISH) test, with chromosome karyotype 46,XY,t(4:5) (q21:q33). PRKG2-PDGFRB fusion was observed by next generation sequencing (NGS) and verified by RT-PCR followed by Sanger sequencing. The results of bone marrow aspiration, bone marrow biopsy, and immunophenotyping showed systemic mastocytosis-related myeloid tumor with basophilia. Interventions: Imatinib 400mg/d was given on the day of admission. Azacitidine 75mg/m(2) was given for induction therapy for 10 days, and followed by one course of DHAG consolidating therapy. Imatinib was taken orally continuously. Outcomes: On the 8th day of treatment, the patient's diet and fatigue improved. The hematological and bone marrow morphological remission was achieved on the 25th day. Cytogenetic complete remission was achieved 3 months later and continued to present (December 20, 2020). PRKG2-PDGFRB fusion gene turned negative 7months later from diagnosis. Lessons: Patients with increased basophilic granulocyte and/or mast cells in peripheral blood and/or bone marrow should be screened for PDGFRB abnormality and myeloid or lymphatic tumor. Patients bearing PDGFRB abnormality have a good response to imatinib.