Mal de Meleda (MDM) is a rare, autosomal recessive form of palmoplantar keratoderma. It is characterized by erythema and hyperkeratosis of the palms and soles that progressively extend to the dorsal surface of the hands and feet. It is caused by mutations in SLURP-1 gene encoding for secreted mammalian Ly-6/uPAR-related protein 1 (SLURP-1). We performed mutational analysis by direct sequencing of SLURP-1 gene in order to identify the genetic defect in three unrelated families (families MDM-12, MDM-13, and MDM-14) variably affected with transgressive palmoplantar keratoderma. A spectrum of clinical presentations with variable features has been observed from the pronounced to the transparent hyperkeratosis. We identified the 82delT frame shift mutation in the SLURP-1 gene in both families MDM-12 and MDM-13 and the missense variation p.Cys99Tyr in family MDM-14. To date, the 82delT variation is the most frequent cause of MDM in the world which is in favour of a recurrent molecular defect. The p.Cys99Tyr variation is only described in Tunisian families making evidence of founder effect mutation of likely Tunisian origin. Our patients presented with very severe to relatively mild phenotypes, including multiple keratolytic pits observed for one patient in the hyperkeratotic area which was not previously reported. The phenotypic variability may reflect the influence of additional factors on disease characteristics.
This report further expands the spectrum of clinical phenotypes associated with mutations in SLURP1 in the Mediterranean population.
Transgressive palmoplantar keratoderma (PPK) is the phenotypic hallmark of Mal de Meleda (MDM, MIM 24300). It is characterized by erythema and hyperkeratosis that extend to the dorsal face of the hands and feet. The disease is distributed worldwide and includes the Mediterranean population. The gene responsible for MDM, ARS (component B) mapped on chromosome 8qter, encodes for the SLURP-1 protein (Ly-6/uPAR related protein-1). A variety of mutations within the ARS gene have been shown to underlie MDM in different populations. Genetic heterogeneity of MDM is suspected. We have recently shown that three different homozygous mutations (82delT, C77R, C99Y) were responsible for MDM in 17 patients from Northern Tunisia belonging to eight unrelated consanguineous families. We report here a Tunisian family with three siblings presenting with recessive transgressive PPK closely resembling the MDM phenotype that excludes linkage to the ARS gene.
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