Background  The pathogenesis of all forms of psoriasis remains obscure. Segregation analysis and twin studies together with ethnic differences in disease frequency all point to an underlying genetic susceptibility to psoriasis, which is both complex and likely to reflect the action of a number of genes.

Materials and methods  In the present study, we performed a family-based association study, and a transmission dysequilibrium test using the PLINK program, in a set of seven Tunisian multiplex families using a panel of 96 single-nucleotide polymorphisms localized in several regions across the genome. Ninety-five of them were reported to be associated with psoriasis in different populations.

Results  Besides the confirmation of association between previous associated regions: 6p, 1p, 2p, 13q, 14q, and 20p, and cutaneous psoriasis, we identified a new association with the rs1249564 in the IL17RD gene.

Conclusion  Our results support the complex genetic basis of psoriasis.