Nagashima-Type Palmoplantar Keratosis: A Common Asian Type Caused by SERPINB7 Protease Inhibitor Deficiency

Nagashima-type palmoplantar keratosis (NPPK) was identified as an autosomal recessive condition prevalent in Asian populations, particularly Japan and China, caused by mutations in the SERPINB7 gene. The study confirmed a founder effect of the c.796C>T mutation in Chinese populations. NPPK was characterized by mild, non-progressive hyperkeratosis on the hands and feet, often accompanied by hyperhidrosis and tinea infections. The mutation was absent in non-Asian populations, suggesting its distribution in Asia due to the founder effect. The findings underscored the role of SERPINB7 in maintaining skin homeostasis and provided insights into the regulatory mechanisms of epidermal proteases and their inhibitors.