Metal allergy and palmoplantar pustulosis

There is controversy surrounding the existence of palmoplantar pustulosis (PPP) and psoriasis as separate clinical entities, or as variants of the same clinical entity. PPP is usually defined as a chronic skin disease characterized by crops of sterile pustules with erythema and sometimes scaling on the palms and soles. PPP has in some studies been associated with autoimmune conditions such as thyroid diseases and celiac disease. Positive patch test reactions to several metals have been documented in patients with PPP, and notably, removal of dental alloys with these metals has been reported in some cases to result in the resolution of skin manifestations, suggesting a causative relationship. PPP is associated with moderate-to-severe discomfort and disability and is difficult to treat, often requiring the use of immunosuppressive agents

Genetic analysis of PSORS1 distinguishes guttate psoriasis and palmoplantar pustulosis

The PSORS1 locus in the major histocompatibility complex region is the major genetic determinant for psoriasis vulgaris. Within the PSORS1 region reside at least three potential candidate genes for psoriasis susceptibility. Specific allelic variants of the genes HLA-Cw*6, HCR*WWCC, and CDSN*5 are strongly associated with psoriasis vulgaris and are in strong linkage disequilibrium with each other. We have genotyped the three psoriasis vulgaris susceptibility alleles of the PSORS1 locus in two clinical variants of psoriasis (guttate psoriasis and palmoplantar pustulosis) to study whether PSORS1 is also involved in the pathogenesis of these variants. We also asked whether these two clinical subgroups could help us to distinguish the causative gene within the high-risk PSORS1 haplotype. The association of guttate psoriasis with the three PSORS1 susceptibility alleles was similar and even stronger than seen with psoriasis vulgaris. Palmoplantar pustulosis, however, did not show association with any of the three candidate genes at this locus. Finally, no correlation with the age of onset for disease was observed. Our results show conclusively that psoriasis vulgaris and guttate psoriasis have a similar genetic basis for their association to PSORS1, whereas palmoplantar pustulosis appears to be a distinct disorder