Recalcitrant Cutaneous Mastocytosis Treated With Genetically Informed Targeted Therapy: A Case Report.

Mastocytosis, a clonal proliferation of mast cells commonly involving the skin and bone marrow, has a varied clinical presentation ranging from cutaneous lesions to systemic disease. Cutaneous mastocytosis is managed symptomatically, but systemic mastocytosis is treated with targeted therapy against the mutated receptor tyrosine kinase c-KIT, the pathogenic driver of mastocytosis. However, there are no guidelines for the treatment of cutaneous mastocytosis refractory to symptomatic management. We herein report a method to select genetically informed therapy for symptomatic and recalcitrant cutaneous mastocytosis. Case presentation: We performed a mutational analysis of dermal mast cells after enrichment by laser capture in a 23-year-old woman with recalcitrant cutaneous mastocytosis. The analysis revealed a aspartic acid to valine substitution at codon 816 (D816V) mutation in the protein c-KIT. Based on these results, we initiated treatment with the multi-kinase/KIT inhibitor midostaurin, a treatment effective against the D816V c-KIT mutation. After 3 months of treatment, the patient exhibited a reduction in the number and size of cutaneous lesions and reported resolution of pruritus and decreased severity of other mast cell-related symptoms. Discussion: The treatment of mastocytosis relies heavily on whether the disease is limited to the skin or systemic. However, there are no guidelines for cutaneous mastocytosis that does not respond to symptomatic management. In the present report describing a patient with recalcitrant cutaneous mastocytosis, we describe a strategy in which skin mutational analysis is used to guide the selection of targeted therapy. Conclusion: Performing mast cell mutational analyses in the skin provides a means to select targeted therapy for symptomatic and refractory cutaneous mastocytosis.