Determination of the relationship between major histocompatibility complex alleles and childhood onset obsessive-compulsive disorder.

BACKGROUND: About half of the cases of obsessive-compulsive disorder (OCD) occurring in childhood/adolescence occur with similar symptoms both in childhood and adulthood. Immunologic stress is claimed to be a risk factor in the etiology of childhood onset OCD. Our aim was to elucidate the relationship between childhood onset OCD risk and MHC complex I and II alleles. METHODS: MHC alleles of 49 OCD children together with 277 healthy children (aged 4-12) were analyzed by PCR. Results were evaluated by using univariate analysis and multivariate logistic regression analysis. RESULTS: A2, A29, C4, DRB3.1, and DRB1*16 alleles were found to increase the risk of OCD. DISCUSSION: The relationship found between DRB locus and OCD in this study was remarkable since there have been studies on different populations reporting similar relationship between DRB locus and rheumatoid arthritis, which is also an AID. MHC class I and class II alleles were found to increase the risk of OCD in our study, which serves as a suitable model for studies suggesting that MHC genes do not work completely independently. Even though the MHC class I and II genes are considered to have different roles in immune response, in fact they tend to work in cooperation. As in previous studies on AIDs, there is a linear relationship between MHC class II alleles and OCD risk.