Delayed-onset pachyonychia congenita associated with a novel mutation in the central 2B domain of keratin 16

A young girl with clinical features of pachyonychia congenita type 1 was un usual in that the typical skin and nail changes were not noted until the ag e of 6 years. Direct sequencing of the KRT16A gene, encoding keratin K16, r evealed a novel mutation K354N in the central 2B domain of the K16 polypept ide. The mutation created a new BsmI restriction site and therefore, the mu tation was confirmed in the patient and excluded from both parents and 50 n ormal, unrelated individuals by BsmI digestion of KRT16A polymerase chain r eaction products. This is the first time a mutation has been described in t his location in a keratin other than K14, where similar mutations cause the milder Weber-Cockayne and/or Kobner types of epidermolysis bullosa simplex .