A rare case of systemic mastocytosis (SM) may imitate the symptoms of eosinophilic enterocolitis, as highlighted in a case published in Gastro Hep Advances.

“Patients with SM, broadly, also have peripheral eosinophilia. Beyond the standard differentials for [eosinophilic gastrointestinal disorders], SM should be the primary differential in patients with a significant past medical history of anaphylaxis,” the authors recommended.

“The occurrence of concomitant cutaneous mastocytosis (urticaria pigmentosa) should always encourage us to consider that systemic manifestation of the disease may be responsible for gastrointestinal dysfunction.”

The patient in the study, a 59-year-old Caucasian female, presented with acute painless bloody diarrhea (10 episodes per day) for the last 2 days as well as chronic urticaria pigmentosa. She was previously diagnosed with eosinophilic enterocolitis 4 years earlier based on histological analysis of colonic and skin biopsies after she presented with nonbloody diarrhea (4 episodes per day for 20 years) as well as a maculopapular rash.

Read more about SM differential diagnosis

The patient had also experienced anaphylactic reactions to anti-inflammatory treatments. In both the earlier and more recent presentations, the patient had eosinophilia with values of >0.5 mm3 on the previous presentation and <1.5 mm3 on the more recent. Colonoscopy revealed cobblestone mucosa which suggested Crohn’s colitis but histology still suggested eosinophilic enterocolitis.

To investigate a more unifying etiology between the cutaneous and gastrointestinal symptoms, serum tryptase levels were tested and found to be elevated (>20 ng/mL). Following this discovery, the colonic samples were immunohistochemically tested and found to be positive for the presence of mast cells.

Based on these new findings, a diagnosis of SM was given according to the World Health Organization’s guidelines requiring a minor (elevated serum tryptase >20 ng/mL) and a major (>15 mast cells in extracutaneous tissues) criteria to be fulfilled. The patient was treated with H1/H2 antihistamines and she experienced rapid cessation of her gastrointestinal symptoms.


Muller TL, Van Der Merwe K, Steele C, Papanikolaou M, O’Dowd G, Parihar V. Systemic mastocytosis imitating eosinophilic enterocolitis. Gastro Hep Advances. 2022;1(3):417-419. doi:10.1016/j.gastha.2022.02.001