Systemic mastocytosis with chronic myelomonocytic leukemia followed by transformation into acute myeloid leukemia

Introduction Systemic mastocytosis (SM) with an associated hematological neoplasm (SM-AHN) constitutes about 40% of all patients with SM. AHN commonly includes myeloid neoplasms and chronic myelomonocytic leukemia (CMML) is seen in about 30% of these patients. Case report A 67-year-old male presented to hematologist with fatigue and significant weight loss. Abdominal ultrasound and computed tomography (CT) detected hepatosplenomegaly, abdominal lymphadenopathy, and ascites. He was anemic with leukocytosis and eosinophilia. Trephine biopsy showed > 30% of spindle-shaped mast cells. The mutation was present. Serum tryptase level was elevated to 62 ng/mL. The patient was diagnosed with aggressive SM and received six cycles of cladribine with partial response. Three years later, he developed severe anemia. Eosinophilia and monocytosis (5.6 × 10/L) were demonstrated in blood film. Hepatosplenomegaly and abdominal lymphadenopathy were also present. Trephine biopsy did not demonstrate the presence of spindle-shaped mast cells, but dysplasia in erythroid and myeloid lineages was evident. The histological result of lymph node biopsy as well as blood and bone marrow findings were in line with CMML. He received hydroxyurea, but he transformed soon into fatal acute monocytic leukemia. Conclusions The prognosis of SM-AHN depends on AHN component. Leukemic transformation of AHN component may occur in a proportion of patients.