RESUMEN
Mastocytosis is a clonal neoplasm with the potential to affect various organs within the body. It can range in clinical severity from benign to extremely aggressive. Mastocytosis can be separated into cutaneous, systemic, and leukemic forms, as well as mast-cell sarcoma and extracutaneous mastocytoma. It is most often an acquired condition but can be inherited; the most commonly identified genetic aberrations leading to mastocytosis are activating mutations involving codon 816 of the KIT gene. Herein, we present the case of a 30-year-old Caucasian man with systemic mastocytosis discovered to have a p.Arg634Trp mutation involving KIT. To our knowledge, this mutation has previously only been identified in children with familial urticarial pigmentosa. Ours is the the first case report in the literature of an adult with systemic mastocytosis likely due to a p.Arg634Trp KIT mutation.