Phacomatosis pigmentokeratotica is a rare syndrome defined by the association of an organoid nevus occasionally with sebaceous differentiation, a speckled lentiginous nevus, and other extracutaneous anomalies. The disorder is a consequence of the so-called twin spot genetic mechanism. We describe the first occurrence involving malignant degeneration of both nevus components, giving rise to three basal cell carcinomas over the sebaceous nevus and a malignant melanoma of the superficial spreading type over the speckled lentiginous nevus. This observation, in concert with the other instances reported in the literature, points to the need for adequate patient follow-up to ensure early detection and treatment of any possible associated malignant degeneration.

BackgroundMultiple familial trichoepithelioma type 1 (MFT1; MIM 601606), a rare monogenic skin disease with autosomal dominant inheritance, is characterized by the development of multiple skin-colored papules on the central area of the face, frequently occurring in the nasolabial area. The disease is associated with various mutations in the cylindromatosis (CYLD; MIM 605018) gene that are also responsible for familial cylindromatosis (FC) and Brooke-Spiegler syndrome (BSS).MethodsRecently we have identified a Spanish MFT1 pedigree with two affected family members (father and daughter). Direct sequencing of the CYLD gene revealed a worldwide recurrent heterozygous nonsense mutation (c.2272C/T, p.R758X) in the patients.ResultsThis mutation has already been detected in patients with all three clinical variants – BSS, FC and MFT1 – of the CYLD-mutation spectrum. Haplotype analysis was performed for the Spanish patients with MFT1, Dutch patients with FC and an Austrian patient with BSS, all of whom carry the same heterozygous nonsense p.R758X CYLD mutation.ConclusionsOur results indicate that this position is a mutational hotspot on the gene and that patients carrying the mutation exhibit high phenotypic diversity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0346-9) contains supplementary material, which is available to authorized users.

NB UV-B phototherapy does not appear to be associated with an increased risk of NMSC.

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