Efficacy and toxicity of hydroxyurea in mast cell activation syndrome patients refractory to standard medical therapy: retrospective case series.

This retrospective case series investigates the efficacy and safety of hydroxyurea (HU) in patients with Mast Cell Activation Syndrome (MCAS) who did not respond to standard treatments. The study involved an electronic chart review of MCAS patients treated with HU, showing that 20 out of 310 patients received HU, with an average age of 42.4 years and a 60% prevalence of dysautonomia. Patients used an average of 10.6 medications before HU, which was administered at an average dose of 634 mg. Over at least two months, patients reported significant reductions in bone pain and gastrointestinal symptoms like bloating, diarrhea, and nausea. Although six patients discontinued HU within six weeks due to adverse events, these were reversible, and continued monitoring helped prevent severe side effects. The study concludes that HU can significantly improve symptoms for refractory MCAS patients with manageable safety concerns.