Cytoreduction is a Valid Option for Treatment and Prevention of Anaphylaxis in Systemic Mastocytosis: Case Report and Literature Review.

Systemic mastocytosis (SM) is a myeloproliferative disorder marked by accumulation of clonal mast cells (MC) and a 100-fold increased risk of potentially life-threatening anaphylaxis not fully preventable with antimediator treatments. Omalizumab can be effective but is off-label and variably available. The effect of cytoreductive treatments such as interferon-alpha, cladribine, and tyrosine kinase inhibitors (TKIs) on anaphylaxis in SM remains unclear. We present a patient with indolent systemic mastocytosis and recurrent life-threatening anaphylaxis despite maximum antimediator treatment and omalizumab who experienced immediate resolution of ongoing anaphylaxis upon initiation of midostaurin treatment. No anaphylaxis recurrence was observed during 25 months of follow-up on midostaurin. A literature review on cytoreduction and anaphylaxis retrieved 18 studies. Despite the limited quality of evidence, a clear trend towards reduction of anaphylaxis-like symptoms was seen across all agents and SM subtypes with resolution and/or improvement noted in 95% of cases with a prior history of anaphylaxis. Immediate resolution of ongoing anaphylaxis observed in our case and the literature suggest cytoreduction can be used for treatment of refractory anaphylaxis and prevention of recurrent anaphylaxis in SM. Further exploration of cytoreduction for these indications is warranted.