A likely case of the indolent type of systemic mastocytosis (SM) was diagnosed endoscopically in a patient with abdominal pain, flushing, and nausea, according to a recent report in the journal Cureus.

The patient was a 39-year-old female with no relevant past medical history. She was initially seen by her primary care provider for dull and nonradiating right lower quadrant pain, paired with extreme flushing of her face, lips, ears, chills, and nausea. At that time, a computerized tomography (CT) scan of the abdomen and pelvis without contrast showed a soft-tissue nodule along the right lower quadrant near the ileocecal region measuring 1.5 by 1.2 cm and 2 mesenteric lymph nodes measuring 1 by 1.4 cm and 1 by 0.7 cm.

Next, the patient presented to a gastroenterology clinic for evaluation of the periappendiceal mass. The physical exam showed no lymphadenopathy and her abdomen was soft, nondistended, and nontender to palpation. There was no sign of organomegaly or abdominal masses.

Laboratory exam showed normocytic anemia (hemoglobin 11.7 g/dL, mean corpuscular volume 90.6 fL), paired with normal complement levels, negative inflammatory markers (C-reactive protein and erythrocyte sedimentation rate), and no electrolyte abnormalities or leukocytosis.

Read more about SM diagnosis

The study authors initially suspected a carcinoid tumor and performed a colonoscopy with endoscopic ultrasound and biopsy. They discovered grade I internal hemorrhoids and 3 sessile polyps in the rectum (6 mm and 10 mm) and transverse colon (22 mm) which were bioptically confirmed to be tubulovillous adenomas.

The colonoscopy exam also found numerous yellow-white mucosal nodules with central hyperpigmentation in the entire colon, as well as discontinuous areas of nonbleeding and ulcerated mucosa in the transverse colon, ascending colon, and cecum.

According to the report, biopsy analysis revealed sheets of eosinophils mixed with clusters of mast cells in the ileal and colonic mucosa, showing atypical morphology, including oval-to-short, spindled nuclei, and focal clustering.

Immunohistochemical stains indicated atypical mast cells positive for CD117, CD25, and tryptase (subset) and negative for CD2 and S100. The clinical diagnosis of SM was supported by OnkoSight NGS KIT sequencing which detected Tier 1 genomic alterations in KIT p.Asp816Val.

The patient was then started on loratadine and famotidine. After some time, another colonoscopy indicated persistent disease.

“In the absence of classical cutaneous lesions, bone marrow suppression, and/or serum tryptase elevation, the diagnosis of indolent SM can be easily missed,” Tagliaferri and colleagues wrote. “As many patients lack cutaneous symptoms at the time of diagnosis, clinical suspicion should remain high if other more common diseases can be excluded.”

The majority of patients with SM have gastrointestinal involvement, yet they are often diagnosed through bone marrow biopsy instead of endoscopy. Indolent SM, marked by both gastrointestinal and cutaneous symptoms in the absence of bone marrow suppression, is extremely rare and often overlooked due to the complexity of the diagnosis.


Tagliaferri AR, Adalja D, Cavanagh Y. A case of systemic mastocytosis diagnosed endoscopicallyCureus. Published on December 8, 2022. doi:10.7759/cureus.32329