RHBDF2 and Non-epidermolytic palmoplantar keratoderma: Tylosis, a genetic disease characterized by hyperproliferation of skin in the palms and soles, loss of hair, and oral leukoplakia [1], is caused by gain-of-function (GOF) mutations (p.I186T, p.P189L, and p.D188N) in the human rhomboid family protein RHBDF2 [1, 2].