# Recurrent Cyclic Vomiting and Gastroparesis-Like Symptoms in a Patient With Mast Cell Activation Syndrome (MCAS): A Case of Gastrointestinal-Predominant MCAS

## TL;DR

A 36-year-old man with unexplained vomiting and delayed stomach emptying was diagnosed with mast cell activation syndrome, a rare condition often mistaken for other disorders.

## Contribution

This case highlights a rare gastrointestinal-predominant presentation of mast cell activation syndrome.

## Key findings

- The patient exhibited delayed gastric emptying consistent with mast cell-mediated dysmotility.
- MCAS was identified as the underlying cause of recurrent vomiting and gastrointestinal symptoms previously misattributed to functional disorders.

## Abstract

Mast cell activation syndrome (MCAS) remains an underrecognized cause of gastrointestinal morbidity, frequently presenting with symptoms indistinguishable from functional disorders. Such diagnostic ambiguity can misdirect management and prolong patient symptoms. Thus, we present a case of a 36-year-old male with MCAS who presented with acute, intractable nausea, vomiting, and left-sided back pain. Examination revealed tachycardia and tenderness in the left costovertebral angle. Laboratory evaluation revealed mild anemia, thrombocytopenia, and slightly elevated bilirubin levels. Abdominal and pelvic CT was unremarkable, and upper endoscopy showed mild mucosal erythema with retained gastric contents. Gastric emptying scintigraphy confirmed delayed gastric emptying consistent with mast cell-mediated dysmotility. This case highlights an uncommon gastrointestinal presentation of mast cell activation, emphasizing the importance of considering MCAS in patients with recurrent unexplained vomiting and delayed gastric emptying.