SHM Converge Scientific Abstract ePoster Gallery-A Clue in the Differential: A Rare Cause of Diarrhea

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An 88-year-old woman with atrial fibrillation, hypertension, chronic anemia, and mild thrombocytopenia presented with worsening diarrhea, nausea, presyncope, weakness, early satiety, and 20-pound weight loss. She had had diarrhea for 1–2 years, worsening to 10–12 loose stools daily. Initial evaluation showed near-baseline cytopenias, monocytosis, lymphopenia, elevated CRP, and mildly elevated alkaline phosphatase. Prior workup had been unrevealing, and she had declined invasive testing in the past.<br /><br />Flexible sigmoidoscopy showed chronic inactive colitis, and biopsy suggested possible microscopic colitis, though atypical. Budesonide did not improve symptoms. Further imaging with MRCP revealed abnormal retroperitoneal and mesenteric lymph nodes suspicious for lymphoma, along with liver and spleen hemosiderosis and splenomegaly. PET scan confirmed multiple hypermetabolic lymph nodes. A lymph node biopsy was unsuccessful, but bone marrow biopsy, elevated serum tryptase, and a KIT D816V mutation established the diagnosis of systemic mastocytosis with an associated hematologic neoplasm: chronic myelomonocytic leukemia (SM-AHN).<br /><br />She was initially treated symptomatically with famotidine, cetirizine, and an epinephrine autoinjector, then escalated to cromolyn for persistent gastrointestinal symptoms. Ultimately, treatment with avapritinib, a tyrosine kinase inhibitor, led to symptomatic improvement.<br /><br />This case highlights that systemic mastocytosis is a rare but important cause of chronic diarrhea, especially when accompanied by cytopenias, weight loss, lymphadenopathy, or allergic-type symptoms. Diagnosis relies on WHO criteria, often requiring bone marrow evaluation and supportive biomarkers such as elevated tryptase and KIT mutations.

Asset Subtitle

Emily L. Jacobson

Meta Tag

Author List Emily L. Jacobson, Julie E. Barrett, Thomas O'Callaghan

Category Clinical Vignettes

Concept Systemic Mastocytosis

Concept Diarrhea

Concept Weight Loss

Concept Cytopenia

Concept Mast Cell Disease

Distinguished Non-Finalist

Presenter Organization University of Michigan

Presenting Author Emily L. Jacobson

Track Adult

Keywords

systemic mastocytosis

chronic diarrhea

chronic myelomonocytic leukemia

KIT D816V mutation

elevated serum tryptase

bone marrow biopsy

lymphadenopathy

weight loss

avapritinib

microscopic colitis

Systemic Mastocytosis

Diarrhea

Weight Loss

Cytopenia

Mast Cell Disease