Low frequency of acetyl salicylic acid hypersensitivity in mastocytosis: The results of a double‐blind, placebo‐controlled challenge study

BACKGROUND: Patients with mastocytosis are at increased risk of anaphylaxis. The use of nonsteroidal anti‐inflammatory drugs (NSAIDs) is often discouraged because of this reason. However, the actual prevalence and severity of NSAID‐related hypersensitivity among patients with mastocytosis is unknown. METHODS: A double‐blind, placebo‐controlled acetylsalicylic acid (ASA) challenge up to a cumulative dose of 520 mg was performed among adult patients with mastocytosis. In addition, a retrospective search of the entire outpatient cohort was performed to obtain “real‐life” data on NSAID hypersensitivity. RESULTS: Fifty patients underwent an ASA challenge. Seventy percent had indolent systemic mastocytosis, 18% had mastocytosis in the skin, and 12% had advanced mastocytosis. The ASA challenge was positive in 1 patient who developed urticaria. The additional retrospective chart review revealed that 8 of 191 patients had a history of NSAID‐related hypersensitivity reaction(s), of whom 3 reported severe systemic reactions. All 8 patients had already experienced NSAID‐related hypersensitivity reactions before mastocytosis was diagnosed. CONCLUSIONS: The frequency of ASA hypersensitivity was 2% in a prospective challenge study and 4.1% in a retrospective chart review of 191 patients with mastocytosis. NSAIDs can be administered safely to most patients with mastocytosis. Extra caution should be taken in patients with a history of hypersensitivity reactions to other drugs, or traditional risk factors for NSAID hypersensitivity.