1 │ INTRODUCTION
BRAFV600E mutations occur in 5% to 16% of pediatric patients with pilocytic astrocytoma, which is the most common type of pediatric brain tumor. This alteration is associated with high recurrence rates, despite conventional chemotherapy, and poor progression-free survival.1–3 The BRAFV600E inhibitors vemurafenib and dabrafenib have demonstrated considerable promise for pediatric patients with relapsed/refractory gliomas harboring theBRAFV600E mutation.4 However, hypersensitivity reactions, such as cutaneous reactions to BRAFV600E inhibitors, are common, even in pediatric patients.5,6 If cutaneous reactions are severe, this leads to permanent discontinuation of a potentially life-saving therapy. Vemurafenib and dabrafenib share similar chemical structures, including a sulfonamide group.5 Cross-reactivity between BRAF inhibitors and other sulfonamides may contribute to their intolerance.5 Hypersensitivity reactions to BRAFV600E inhibitors followed by tolerance to another BRAFV600E inhibitor is rarely described, especially for pediatric patients. To date, successful transition from one BRAFV600E inhibitor to another is reported in only one pediatric case of anaplastic ganglioglioma and in three adult cases of melanoma.7–10 Here, we describe an immediate hypersensitivity reaction to vemurafenib in a pediatric patient with a pilocytic astrocytoma. We then administered a desensitization regimen with dabrafenib and trametinib, which yielded a positive tumor response without further allergic reaction.