Evidence for a Novel Psoriasis Susceptibility Locus at 9q33–9q34 in Chinese Hans

Psoriasis is a heterogeneous disease for which nine linkage loci (PSORS loci 1–5 and PSORS7–10) have been accepted by the Human Genome Nomenclature Committee and an additional 16 potential susceptibility loci have been reported so far. Our previous genome-wide scan in 61 Chinese Han psoriasis vulgaris families found two susceptibility loci at 6p21.3 and 4q31 and additional suggestive linkage evidence at other regions, including 9q33. In this follow-up study, the linkage evidence at 9q33 was further investigated using an expanded sample of 160 families and improved marker coverage. Our follow-up linkage analysis of the 160 families demonstrated strong linkage evidence (P≤0.000022) throughout a region between 133.38 and 146.23 cM with a maximum nonparametric linkage (NPL) score of 4.64 (P=0.00000023) and a heterogeneity LOD (HLOD) score of 5.03 (α=46%) at 142.39 cM near the marker D9S290. By stratifying the 160 families into the subtypes of 130 early-onset and 30 late-onset families, we revealed stronger linkage evidence in the early-onset psoriasis families with a maximum multipoint HLOD score of 6.48 (α=58%) and a maximum NPL score of 4.69 (P=0.00000012) near marker D9S290. Our follow-up study has confirmed a novel susceptibility locus at 9q33–34 for early-onset psoriasis in the Chinese population.