Palmoplantar keratoderma, Nagashima type

Palmoplantar keratoderma, Nagashima type (PPKN) is a rare inherited skin disorder characterized by diffuse, non-progressive thickening of the skin on the palms of the hands and soles of the feet (palmoplantar keratoderma). It was first described in Japanese populations and is considered one of the most common forms of hereditary palmoplantar keratoderma in East Asian countries, particularly Japan and China. The condition is caused by mutations in the SERPINB7 gene, which encodes a serine protease inhibitor expressed in the skin. The keratoderma in Nagashima type is typically milder than other diffuse forms and has a distinctive reddish (erythematous) appearance. The thickened skin characteristically extends beyond the palms and soles onto the dorsal surfaces of the hands and feet, known as a "transgrediens" pattern. Mild hyperhidrosis (excessive sweating) of the affected areas may also be present. The skin changes are usually noticed in infancy or early childhood and tend to remain stable throughout life without significant progression. The condition primarily affects the skin and does not involve other organ systems. There is currently no cure for palmoplantar keratoderma, Nagashima type. Treatment is symptomatic and supportive, focusing on the use of emollients, keratolytic agents (such as urea-based or salicylic acid-based creams), and regular mechanical debridement to reduce skin thickness and improve comfort. The condition is generally benign and does not significantly impact life expectancy. Genetic counseling is recommended for affected families to understand the inheritance pattern and recurrence risk.

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