Clinical and molecular investigation of Buschke-Fischer-Brauer in consanguineous Tunisian families

Abstract

Background: Punctate palmoplantar keratoderma type I (PPPK-BFB), also called Buschke-Fischer-Brauer disease (MIM 148600) is a rare autosomal dominant disorder of keratinization, characterized by multiple hyperkeratotic lesions on the palms and soles. Recently, PPPK-BFB has been shown to be associated with mutations in the AAGAB gene in several families of European, African, Canadian and Asian origins.

Objective: To characterize the clinical and genetic features of PPPK-BFB in a broad group of Tunisian patients.

Methods: Epidemiological and clinical data were collected from 18 PPPK-BFB patients belonging to eight Tunisian families. We carried out mutational and structural analysis for families not previously investigated.

Results: Sequencing of the remaining families identified a total of three different mutations in AAGAB gene: one founder mutation (c.348_349delAG, p.R116Sfs*1) specific to the inbred Tunisian population, one recurrent mutation and (c.370C>T, p.R124*) one novel variant (c.430C>G, p.E144K). This novel mutation, involving a conserved amino acid, is predicted to be probably damaging to the p34 protein function. Assessment of the phenotypic presentation of this group of Tunisian patients was marked by variable severity and varying age at onset with a possible presence of anticipation noted in five out of eight families (62.5%). There is no apparent genotype-phenotype correlation. Despite the high degree of inbreeding, no homozygous individuals for AAGAB mutations were observed. Homozygous carriers in AAGAB gene are likely non-viable.

Conclusion: This study contributes to further characterize PPPK-BFB in consanguineous families and to extend the mutational spectrum of AAGAB gene in the Tunisian population.