Identification of sporadic mutations in the helix initiation motif of keratin 6 in two pachyonychia congenita patients: further evidence for a mutational hot spot

Pachyonychia congenita (PC) is a rare, autosomal dominant, ectodermal dyspl asia characterized most distinctly by the presence of symmetric nail hypert rophy, In the Jadassohn-Lewandowsky form, or PC-1, additional cutaneous man ifestations may include palmoplantar hyperkeratosis, hyperhidrosis, follicu lar keratoses, and oral leukokeratosis. Mutations have previously been iden tified in the 1A helix initiation motif of either keratin 6 or keratin 16 i n patients with PC-1, In the current study, we have identified 2 sporadic, heterozygous mutations in the IA helix region of the K6 isoform (K6a), The first mutation identified was a 3 base pair deletion (K6a Delta N171), The second mutation was a C-to-A transversion resulting in an amino acid substi tution (K6a N171K). These data, in combination with previous reports, provi de further evidence that this location is a mutational hot spot.