Pachyonychia congenita Authors: Professors

Pachyonychia congenita (PC) is a rare genodermatosis affecting the nails and other ectodermal tissues. It is mainly characterized by gross thickening of all finger and toe nails. Different additional clinical features are observed; they fit into two major types: the Jadassohn-Lewandowsky and the Jackson-Lawler syndrome. The condition is usually transmitted as an autosomal dominant trait, though recessive forms have been described. A purely clinical classification does not correlate satisfactorily with the observed phenotypic expression in most reported cases. Actually it has been recognized that molecular genetic analysis helps the clinical distinction in subtypes. PC type I is due to mutations in the KRT16 gene encoding keratins K6a and K16, type II is caused by mutations in the KRT17 gene encoding keratin 17. The only effective treatment for nail lesions is surgery with radical excision of the nail, nail bed, and nail matrix and skin implantation at the site of the removed nail. The most recent literature refers to descriptions of about 250 cases up until 1993.