Background: Interleukin (IL) 19, IL-20 and IL-24 belong to the IL-10 cytokine family and have been identified to play a role in the regulation of epidermal functions and in inflammation. The genes encoding IL-19, IL-20 and IL-24 are located within a gene cluster on chromosome 1q31-32 and carry frequent genetic variations.
Objectives: This study investigated whether variations in the IL19, IL20 and IL24 genes that have previously been associated with plaque-type psoriasis may also play a role in palmoplantar pustulosis (PPP).
Patients: Fifteen polymorphisms were analysed in 43 patients with PPP and in 149 healthy control subjects.
Results: The rare allele of IL20 1380 A-->G (rs2981573) was less frequent in patients with PPP compared with healthy controls (OR 1 x 95, 95% CI 1 x 00-3 x 79). Haplotype analyses of IL19 and IL20 suggested an increased risk for PPP associated with IL20 haplotype GAA (OR 2 x 39, 95% CI 1 x 17-4 x 86) and a reduced risk for PPP associated both with IL19 haplotype GATGATA (OR 0 x 41, 95% CI 0 x 16-1 x 05) and IL20 haplotype GGG (OR 0 x 48, 95% CI 0 x 23-0 x 98). Extended haplotype analysis revealed an association of IL19/IL20 haplotype GACACCGGAA with a higher risk for PPP (OR 2 x 31, 95% CI 1 x 05-5 x 10) and of IL20/IL24 haplotype CAAAC with a reduced risk for PPP (OR 0 x 12, 95% CI 0 x 02-0 x 82).
Conclusions: This exploratory study supports the hypothesis that variations of genes of the IL-19 subfamily of cytokines influence susceptibility to PPP. However, due to the limited size of the study samples, this current concept should be considered as preliminary and the results need to be confirmed in future independent studies.