A healthy 2-months-old boy presented at our pediatric dermatology consultation with a history of dry and scaling skin on his palms and soles since birth. There were no other skin abnormalities and family members did not mention any similar dermatological problems in the past. Emollients and keratolytic creams were applied daily but because of ongoing scaling and the development of an erythematous border around the lesions, a skin biopsy was performed. This biopsy showed marked hyperkeratosis, enlarged keratohyalin granules in the upper epidermal layers and perinuclear vacuolization of the keratinocytes. These histopathological findings together with the demonstration of a de novo c.487C>T mutation in the gene coding for keratin 9, confirmed the diagnosis of epidermolytic palmoplantar keratoderma (EPPK).
Palmoplantar keratodermas, hereditary or acquired, are a large and heterogeneous group of disorders characterized by gross thickening and/or hyperkeratosis of the palmoplantar skin. EPPK is an autosomal dominant genodermatosis, first described by Vörner in 1901 and manifesting shortly after birth. It is one of the most frequent types of hereditary palmoplantar keratoderma with a worldwide incidence of 2.2 to 4.4 per 100.000 newborns. There is a well-demarcated hyperkeratosis of the palms and soles with a yellowish discoloration and marginal erythema. Other possible features include itch, scaling, camptodactyly, knuckle pads, nail alterations, hyperhidrosis, decreased heat sensitivity and low resistance to physical trauma. EPPK is generally caused by a keratin 9 (KRT 9) gene missense mutation, and more rarely by keratin 1 (KRT 1) gene mutations, exclusively expressed in palmoplantar epidermis and responsible for the structural integrity of the skin. The diagnosis of EPPK might be challenging due to its clinical heterogeneity early in life, and therefore molecular diagnosis is important. Treatment must focus on keratolytics that soften the palms and soles, to control discomfort and improve functionality.
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G. Leemans1, K. Keymolen2, L. De Raeve1
Department of Dermatology1 and Medical Genetics2, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel.