The A5.1 allele of the major histocompatibility complex class I chain-related gene A is associated with psoriasis vulgaris in Chinese.
BACKGROUND: Recent studies have demonstrated an association of a polymorphic (GCT)n triplet repeat in the transmembrane (TM) region of the major histocompatibility complex (MHC) class I chain-related gene A (MICA), one of the MHC class I chain-related (MIC) family members, with some autoimmune diseases, including Behçet's disease, acute anterior uveitis, Takayasu's arteritis and others. OBJECTIVES: The aim of this study was to examine whether the MICA gene is associated with psoriasis vulgaris (PS) in Chinese. PATIENTS AND METHODS: The (GCT)n polymorphism of the MICA gene was investigated in 200 healthy Chinese of Han origin and 300 patients with PS by polymerase chain reaction amplification and denaturing polyacrylamide gel electrophoresis. RESULTS: Five alleles, namely A4, A5, A6, A9 and A5.1 were found in both groups. Comparison of the data from both groups revealed that the A5.1 allele was present at a significantly higher frequency in the patient group (41.5%) than in the control group (23.0%) (Pc < 0.0001, Pc means the probability of a comparison with the control group). The frequency of A5.1-positive cases was also significantly increased in the patient group (68.0%) as compared with the controls (38.0%) (Pc < 0.0001). Furthermore, the carrier frequency of A5.1-positive was significantly increased in psoriatic patients with a positive family history and with early onset as compared with sporadic cases (Pc = 0.0005) and with late onset PS (Pc = 0.002). CONCLUSIONS: These results suggest that the MICA gene may be associated with the development of PS in Chinese.