Pachyonychia congenita (PC) is a genodermatosis caused by mutations in keratin genes. PC type 1 (Jadassohn-Lewandowsky) involves which keratins and has which hallmark clinical feature?

• A KRT1/KRT10 mutations; palmoplantar hyperkeratosis with blistering
• B KRT6a/KRT16 mutations; massive subungual hyperkeratosis (wedge-shaped nails) and painful plantar keratoderma ✓
• C KRT5/KRT14 mutations; skin fragility and mechanobullae
• D KRT9 mutations; epidermolytic PPK without nail changes

Explanation

PC type 1 (now simply called PC-K6a or PC-K16 per updated classification) is caused by mutations in KRT6a or KRT16, expressed in nail epithelium and suprabasal palmoplantar epidermis. The hallmark is massive subungual hyperkeratosis producing characteristic wedge-shaped, thickened, discoloured nails, combined with painful plantar keratoderma. KRT5/KRT14 mutations cause EB simplex; KRT1/KRT10 cause epidermolytic ichthyosis; KRT9 causes epidermolytic PPK (Vorner's).

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.