P23 Successful Control of Systemic Mastocytosis Symptoms in a Two-Year-Old with Omalizumab

Abstract

Abstract A 6-month-old boy presented to us with diffuse cutaneous mastocytosis, experiencing constant severe pruritus, blistering, urticaria, flushing, diarrhoea, and frequent anaphylaxis episodes. He was found to have hepatosplenomegaly and mast cells in the bone marrow aspirate, confirming systemic mastocytosis. His tryptase was significantly elevated (87 ug/ml). A c-KIT D816V mutation was identified in exon 17 through a skin biopsy and peripheral blood testing. The patient received concomitant treatment with cetirizine (eightfold dosage), hydroxyzine, chlorphenamine, cimetidine, ketotifen, sodium cromoglicate, and montelukast in addition to topical treatment. Despite the treatment, he continued to have frequent episodes of flushing, anaphylaxis, blisters, and severe pruritus. He required oral prednisolone on several occasions, which provided little relief. Treatment with Imatinib was not an option, as patients with mastocytosis who have the c-KIT D816V mutation do not respond to it. Due to his poor quality of life, we initiated monthly injections of omalizumab (150 mg sc). After three doses, his DLQI score decreased from 29/30 to 10/30. He had no further anaphylactic episodes, and he had significant reduction in the episodes of flushing, urticaria and blistering. Unfortunately, there was little improvement in his pruritus, which remains troublesome for him, particularly at night. He had no significant side effects of omalizumab. Conclusion Omalizumab may provide safe and effective management of symptoms in paediatric patients with systemic mastocytosis, refractory to high-dose conventional therapy, particularly in patients who cannot receive imatinib.