A 72-year-old female was diagnosed with c-kit-positive ISM. She had no cutaneous manifestations of mastocytosis. Her initial presentation was that of Hymenoptera anaphylaxis, with flushing, palpitations, and loss of consciousness (). She was treated with cetirizine and ranitidine but continued to experience occasional facial flushing, vomiting, lightheadedness, drenching night sweats, and bone pain. Given her history of venom anaphylaxis, omalizumab was started at 300 mg every 4 weeks () for 14 months followed by rush venom desensitization [, ]. Symptoms of her underlying ISM resolved completely on ongoing omalizumab therapy. Tryptase had also fallen from 40.5 to 36.8 ng/ml.
A 32-year-old male with lesions of urticaria pigmentosa was diagnosed with c-kit-positive ISM. During the summer of 2015, while working outside, he experienced 3 Hymenoptera stings resulting in immediate onset of flushing and presyncope (). In spite of administration of epinephrine, he developed nausea and vomiting, generalized hives, and worsening presyncope. He was resuscitated in an emergency department but continued to experience daily diarrhea, numbness, and tingling sensation in his extremities, night sweats, severe headaches, and flushing upon strenuous physical activity. Because the symptoms were refractory to a combination of cetirizine, ranitidine, montelukast, and cromolyn, he was started on omalizumab 300 mg at 4-week intervals (). A follow-up 8 months later revealed improved symptomatic control and a fall in tryptase from 42.2 to 34 ng/ml (). However, he has continued to experience intermittent itching, flushing, and diarrhea. A follow-up in late 2018 revealed that he had chosen to discontinue omalizumab, with continued control of disease.