Punctate palmoplantar keratoderma type I: the clinical and genetic features of two family members with AAGAB gene mutation

Lanyu Sun, Serviço de Dermatologia, Unidade Local de Saúde Santa Maria, Lisbon, Portugal Leonor Lopes, Serviço de Dermatologia, Unidade Local de Saúde Santa Maria, Lisbon, Portugal Pedro de Vasconcelos, Serviço de Dermatologia, Unidade Local de Saúde Santa Maria, Lisbon, Portugal Luís Soares-de-Almeida, Serviço de Dermatologia, Unidade Local de Saúde Santa Maria; Clínica Universitária de Dermatologia, Faculdade, Medicina da Universidade de Lisboa; Lisbon, Portugal Gabriel Miltenberger-Miltenyi, IMM João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal Joana F. Ferreira, Unidade de Saúde Familiar Monte Crasto, Unidade Local de Saúde Santo António Porto, Portugal Paulo Filipe, Serviço de Dermatologia, Unidade Local de Saúde Santa Maria; Clínica Universitária de Dermatologia, Faculdade, Medicina da Universidade de Lisboa; IMM João Lobo Antunes, Faculdade de Medicina, Universidade de Lisboa. Lisbon, Portugal

Hereditary punctate palmoplantar keratoderma type I (PPPK1) is a rare autosomal dominant disorder characterized by hyperkeratotic papules on the palms and soles, typically appearing in adolescence but occasionally manifesting later in life. We describe two family members, an African woman (61 years old) and her daughter (29 years old), presenting with multiple asymptomatic hyperkeratotic papules on the palms and soles. Histopathology revealed orthohyperkeratosis, acanthosis, hypergranulosis, and elongated rete ridges. Genetic analysis identified a heterozygous c.535+1G>A mutation in the AAGAB gene. Despite topical salicylic acid, urea, and tretinoin treatment, only minimal improvement was observed. PPPK1 pathogenesis involves genetic factors, with AAGAB being a major contributor, although other loci may be implicated. These cases highlight the phenotypic variability and delayed disease onset in some individuals, underscoring the need for further investigation into the underlying genetic mechanisms and effective treatment strategies.

Keywords: Punctate palmoplantar keratoderma. Hereditary keratodermas. AAGAB mutation.