TRPV3 and epidermolytic palmoplantar keratoderma, 1: Olmsted syndrome is characterized by symmetrically distributed, destructive, inflammatory palmoplantar keratoderma with periorificial keratotic plaques, most commonly due to gain-of-function mutations in the transient receptor potential vanilloid 3 (TRPV3) gene, which involves multiple pathological functions of the skin, such as hyperkeratosis, dermatitis, hair loss, itching, and pain.