Aggressive systemic mastocytosis presenting as rapidly progressive ascites, generalised lymphadenopathy and osteosclerosis.

Rapidly progressive ascites is a frequent clinical manifestation of advanced abdominal malignancies or portal hypertension due to liver diseases. We report a case of 61-year-old man who presented with rapidly progressive ascites. The presence of ascites, generalised lymphadenopathy, osteosclerosis on imaging and hepatosplenomegaly initially pointed towards the diagnosis of advanced high-grade lymphoma or accelerated myeloid neoplasm. Lymph node biopsy revealed infiltration by CD45, cKIT and CD30; tryptase and toluidine blue-positive mast cells (MCs). Bone marrow examination revealed infiltration by MCs and next generation sequencing revealed the pathognomic exon 17 D 816V KIT mutation. The patient was started on weekly pegylated interferon with significant symptom relief. Systemic mastocytosis should be considered as a differential diagnosis in a clinical case of ascites of unknown aetiology even in the absence of typical skin manifestations.