Hundreds of genodermatoses show changes of the nails, most commonly among the ectodermal dysplasias. Among the more common nail disorders are: (i) pachyonychia congenita, a group of disorders caused by mutations in one of five keratin genes expressed in the nail matrix, which also features painful plantar keratoderma; (ii) dyskeratosis congenita, characterized by telomerase shortening leading to nail dystrophy, oral leukoplakia and poikiloderma with a high risk of bone marrow failure; (iii) nail–patella syndrome resulting from mutations in the LIMX1b transcription factor that disrupt the development of the nails, patella, elbow, pelvis and kidneys; and (iv) hereditary anonychia, due to mutations in
R‐spondin 4
.