Postzygotic HRAS mutation causing both keratinocytic epidermal nevus and thymoma and associated with bone dysplasia and hypophosphatemia due to elevated FGF23.

Introduction: Epidermal nevus syndrome is a rare group of disorders characterized by the combination of congenital epidermal nevi and extracutaneous features, including skeletal, neurological, ocular, and other systemic findings. We report a case of keratinocytic epidermal nevus syndrome that includes a thymoma, bone dysplasia, and hypophosphatemia with elevated fibroblast growth factor 23 (FGF23) levels associated with postzygotic HRAS mutation.

Case Report: A 14-year-old boy was admitted due to recent limping.