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HLA-Cw6 is strongly associated with psoriasis and has been suggested to be the PSORS1 gene that confers susceptibility to early-onset psoriasis. In this study of the clinical features of HLA-Cw*0602-positive and -negative psoriasis patients in a Han Chinese population, we typed HLA-C in a cohort of 679 patients and compared the two groups. Cw*0602-positive patients (n=345) had an earlier disease onset (p < 1 x 10(-5)), more severe disease (p < 1 x 10(-3)), higher frequency of guttate psoriasis (p < 1 x 10(-9)), more affected legs and trunk (p < 1 x 10(-5)), higher incidence of Kobner's phenomenon (p=0.005) and of trauma history (p=0.009). Cw*0602-negative patients (n= 334) had more palmoplantar pustulosis (p=0.004), nail changes (p=0.001) and scalp involvement (p=0.007). However, there was no statistically significant difference between the two groups regarding age, gender, incidence of plaque psoriasis, erythrodermic, inverse, psoriatic arthritis, and the precipitation factors stress and infection. The study showed that Cw*0602-positive patients had some obvious clinical differences from Cw*0602-negative patients in a Han Chinese population, which provides evidence for an HLA-Cw*0602-associated phenotype in psoriasis.

Vitiligo vulgaris is an acquired depigmenting disorder resulting from the loss of melanocytes in the skin. Though several putative susceptibility loci of vitiligo have been identified in different populations, the pathogenesis of the disease remains poorly understood. Through genetic linkage analysis of a large Chinese family cohort of vitiligo, we identified a vitiligo linkage locus AIS4 within chromosome 4q12-q21, a region containing several possible candidate genes, including the platelet-derived growth factor receptor alpha (PDGFRA) gene. We postulated that PDGFR mutations may be linked with vitiligo. To test this hypothesis, we performed DNA sequencing on this gene in 143 multiplex families with familial vitiligo vulgaris, 480 patients with sporadic vitiligo vulgaris, and 480 healthy subjects. Mutations were found in 3.5% of familial vitiligo cases, which is significantly higher than for the general population (0.42%, p = 0.008, Fisher's exact test), and possibly higher than in sporadic vitiligo patients (1.0%, p = 0.053). To our knowledge, this is the first observation that PDGFRA mutations are linked with familial vitiligo vulgaris.