Molecular diagnosis of Nagashima-type palmoplantar keratoderma

Nagashima-type palmoplantar keratoderma (PPKN; OMIM # 615598) is an autosomal recessive diffuse palmoplantar keratosis, first described by Nagashima in 1977. Clinically, PPKN shows well-demarcated diffuse erythematous hyperkeratosis on the palms and soles, often with hyperhidrosis. The skin lesions develop within the first few years of life and gradually progress until the late teens. Histopathological examination of the erythematous skin reveals orthokeratotic hyperkeratosis with acanthosis and hypergranulosis. Responsible gene for PPKN has very recently been identified as SERPINB7. So far, only few mutations in SERPINB7 have been reported, with highly predominant nonsense mutation suggested to be a founder mutation in Asian populations.