Background: The mast cell is a common tissue cell located in connective tissue around blood vessels and beneath the capsular tissues of most organs. Uncontrolle proliferation can lead to mast cell disease, which may have different clinical presentation depending on site of primary involvement. Recently, a point mutation in the c-kit receptor gene, Asp816Val (D816V), was shown to activate c-kit, via ligand-independent receptor autophosphorylation resulting in uncontrolled mast cell proliferation. Fusion gene involving Fip1-like 1(FIPL1L1) and plateletderived growth factor receptor α (PDGFRA) was identified in hypereosinophilic syndrome (HES) and mast cell disease. These mutations might have quite different treatment response to imatinib mesylate.
Case Report: A 71-year-old man presented with intractable ascites, hepatosplenomegaly, and skin ecchymosis change. Laboratory tests showed leukocytosis, monocytosis, and anemia. Histopathological examination of bone marrow, liver, skin, and ascites all showed spindle-shaped mast cells infiltration. Gene mutation analysis revealed one nucleotide deletion in PDGFRA exon18; the frame-shift generating a new mutated protein. The patient was treated with hydroxyurea. His ascites and leukocytosis were under controlled.
Conclusions: Systemic mastocytosis should be considered as one cause of ascites, especially in those patients with unexplained hepatomegaly and splenomegaly. Genetic analysis is crucial in this kind of cases in order to determine the treatment strategy and evaluate patients’ prognosis.

Keywords: systemic mastocytosis, Chronic myelomonocytic leukemia, Hepatosplenomegaly, platelet-derived growth factor receptor α [PDGFRA]