Pediatric Mast Cell Activation Syndrome

RATIONALE: Patients with mast cell activation syndrome(MCAS) have symptoms consistent with mast cell mediator release, elevation of mast cell(MC) mediator(s) and symptomatic resolution following medications that block MC mediator effect(s). MC mediator levels in pediatric mast cell disorders are unknown. Our hypothesis is that the pattern of mast cell mediator(s) elevation in pediatric MCAS resembles adult MCAS.

METHODS: A retrospective chart review of 104 children who underwent evaluation for MCAS (2015-2017) was performed. Levels of serum tryptase, urinary n-methyl-histamine(n-MH), 2,3-dinor11β-prostaglandin-F_2α(PG-D₂), and leukotriene E4(LTE4) are reported.

RESULTS: Thirty-two patients had ≥1 elevated urine MC mediators, based on established adult reference intervals. Of this total, 1 patient had systemic mastocytosis, 4 patients had cutaneous mastocytosis, and 6(6%) patients had MCAS. The average age at diagnosis was 9±5years. Serial testing in two patients with normal baseline revealed an elevated urine mast cell mediator level during an episode; one of those patients (with suspected familial hypertryptasemia) had PG-D2 elevation and the other LTE4 elevation. Five patients (83%) had at least 2 elevated MC mediators. More patients had an elevated PG-D₂ (n=5) compared to serum tryptase(n=2). There was a greater percentage of patients that had elevated PG-D₂ compared to an elevated serum tryptase for flushing(80-vs-50%), diarrhea(100-vs-100%), and abdominal pain(100%-vs-50%). There was a greater percentage of patients with elevated tryptase compared PG-D₂ for pruritus(100-vs-60%) and urticaria(50-vs-40%).

CONCLUSIONS: Urinary PG-D₂ is the most frequently elevated product in our pediatric MCAS cohort, resembling adult MCAS. We recommend measurement of all MC mediators in patients with symptoms suggestive of MCAS.