Aggressive Systemic Mastocytosis Presenting as Cryptogenic Cirrhosis, Refractory Ascites, and Cytopenias: A Case Report

Abstract

Aggressive systemic mastocytosis (ASM) is a rare clonal mast cell neoplasm characterized by extracutaneous mast cell infiltration leading to progressive organ dysfunction. Hepatic involvement is uncommon but clinically significant, as it may manifest with portal hypertension and refractory ascites, closely mimicking cryptogenic cirrhosis; thereby, contributing to diagnostic delay. In this report, we present a case of ASM with predominant hepatic involvement and associated cytopenias, underscoring the clinical, laboratory, and histopathologic features critical to establishing the diagnosis.

A 77-year-old Thai man presented with a 6-month history of progressive abdominal distension, early satiety, and significant unintentional weight loss. He initially received a diagnosis of cryptogenic cirrhosis with portal hypertension. Laboratory evaluation revealed normocytic anemia, thrombocytopenia, hyperglobulinemia, and isolated elevation of alkaline phosphatase with preserved hepatic synthetic function. Imaging studies demonstrated cirrhotic liver morphology, splenomegaly, generalized lymphadenopathy, and large-volume ascites. Bone marrow biopsy showed hypercellular marrow with spindle-shaped mast cell infiltration expressing CD117, mast cell tryptase, CD2, and CD30. Liver biopsy demonstrated sinusoidal infiltration by atypical mast cells with concordant immunophenotypic features. Serum tryptase was markedly elevated, and the KIT D816V mutation was detected, confirming the diagnosis of ASM. The patient developed refractory ascites requiring repeated therapeutic paracentesis and was subsequently treated with midostaurin, resulting in substantial clinical improvement, resolution of ascites, weight gain, and partial hematologic recovery.