Painful Thickened Skin on the Soles of the Feet

A 45-year-old man from Tonga presented with a 20-year history of painful calluses, fissures on the soles, nail thickening, and intermittent white patches in the oral cavity. Physical examination revealed thick, yellow hyperkeratotic scales on the feet and hypertrophic nail dystrophy. Genetic testing confirmed a diagnosis of pachyonychia congenita (PC) due to a mutation in the keratin gene KRT16. PC is an autosomal dominant disorder caused by mutations in keratins 6A, 6B, 6C, 16, and 17. Alopecia is not typically associated with PC, unlike other genodermatoses such as Clouston syndrome. The case highlights the importance of genetic testing in diagnosing PC and differentiating it from other similar conditions.