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Original Research Open Access
Volume 7 | Issue 1 | DOI: https://doi.org/10.33696/Gastroenterology.7.079

Features of Pediatric Patients with Clinically Diagnosed Mast Cell Activation Syndrome

  • 1Food Allergy Center and Pediatric Allergy Immunology, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA
  • 2Department of Pathology, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA
  • 3Division of Pediatric Allergy, Immunology, and Rheumatology, Department of Pediatrics, Linkou Chang Gung Memorial Hospital and Chang Gung University, Taoyuan, Taiwan
  • 4Food Allergy Center and Pediatric Gastroenterology and Nutrition, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA
  • #Authors contributed equally
+ Affiliations - Affiliations

Corresponding Author

Qian Yuan, qyuan@mgh.harvard.edu

Received Date: August 14, 2026

Accepted Date: September 07, 2026

Abstract

Background: Mast cell activation syndrome (MCAS) is a heterogeneous disorder with diverse clinical manifestations, making diagnosis and management challenging. Pediatric MCAS remains poorly characterized, and the applicability of current diagnostic criteria in children is uncertain. Our objective is to evaluate the clinical history, laboratory findings, intestinal biopsy results, and treatment patterns of pediatric patients with a clinical diagnosis of MCAS, and to identify features that may improve diagnosis and management.

Methods: In this retrospective study, we reviewed patients younger than 18 years with MCAS documented in clinical notes from the Massachusetts General Hospital and Brigham and Women’s Hospital databases. Clinical history, symptoms, laboratory data, and intestinal mucosal biopsy reports were collected and analyzed. Symptoms were grouped by category, and incidence rates were calculated.

Results: Many pediatric patients with a clinical diagnosis of MCAS did not meet the current elevated tryptase cutoff of 11.2 ng/mL, yet showed multisystem symptoms consistent with histamine release and responded clinically to MCAS treatment. Cutaneous and gastrointestinal symptoms were most common (>70%). Many patients also had increased intestinal mucosal mast cells on CD117 staining despite tryptase levels below 11.2 ng/mL. Common treatments included H1/H2 antihistamines, cromolyn, and ketotifen, with benefit reported in 95% of cases.

Conclusion: The current tryptase cutoff for MCAS diagnosis may not be optimal for children. CD117 staining of intestinal mucosal biopsies may aid diagnosis. Clinical manifestations and treatment patterns in pediatric MCAS appear similar to those reported in adults.

Keywords

HATS, Mast cell activation syndrome, Tryptase, Pediatric cohort, Diagnosis, Symptomology, CD117+ mast cells

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