A 49-year-old woman was diagnosed with c-kit-positive ISM with tryptase 11.4 ng/ml (). Symptoms of SM included daily headaches, sporadic flushing, itchy throat, mild coughing, loose stools, lightheadedness, and palpitations. No cutaneous manifestations of mastocytosis were observed. She was markedly intolerant to exercise, heat, and strong emotion, all of which triggered the symptoms in spite of medications, which included ranitidine, loratadine, cetirizine, ketotifen, and montelukast. In early 2017, she experienced 5 anaphylactic reactions, requiring emergency department visits and treatment with epinephrine as well as 5 milder reactions managed at home (). Omalizumab was started at 300 mg at 4-week intervals (). On omalizumab, multisystem reactions were entirely suppressed, with only breakthrough flushing once per week, loose stools roughly twice per month, and occasional lightheadedness. A follow-up one year later revealed complete resolution of symptoms with no adverse reactions to her medications and reduced tryptase to 8.3 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.