A Rare Case of Systemic Mastocytosis With Associated Clonal Hematological Non-Mast Cell Lineage Disease That Transformed to Acute Leukemia With IDH2 Mutation.

An elderly 72-year-old man presented with anemia, thrombocytopenia, monocytosis, splenomegaly and lymphadenopathy. Bone marrow biopsy was consistent with mast cell neoplasm with positive CD117, CD25, CD34 myeloblasts and polymerase chain reaction (PCR) revealed mutation of D816V. He developed bilateral femoral neck fractures and biopsy confirmed that he has systemic mastocytosis (SM). He received cladribine and midostaurin with stable disease for 21 months. His SM with associated clonal hematological non-mast cell lineage disease (SM-AHNMD) transformed to acute myelogenous leukemia with isocitrate dehydrogenase 2 (IDH2) mutation. A trial of enasidenib was given for 5 months but without any response. Patient decided to go with home hospice and died afterwards.