576 Hla and Chronic Urticaria with Positive Autologous Serum Skin Test among Brazilians

BACKGROUND: Many autoimmune diseases are associated with certain alleles of the human leukocyte antigen (HLA) system, and recent studies have shown that, in many cases, chronic urticaria has autoimmune etiology. An association between class I and II alleles of the major histocompatibility complex (MHC) and idiopathic chronic urticaria (ICU) has previously been observed in different populations, but there are still no studies on Brazilian populations in this respect. The involvement of MHC classes I and II (loci A, B and DR) in Brazilian patients with ICU and a positive autologous serum skin test (ASST) was investigated and compared with a healthy population group. METHODS: DNA was extracted from the blood of 42 patients with ICU (28 women; mean age ± SD: 44 ± 12 years; range: 19 to 88 years) and MHC classes I and II alleles were determined using the polymerase chain reaction (PCR) and a laboratory test for oligonucleotide hybridization using a single-filament probe. The frequencies of these alleles in patients with chronic urticaria were compared with the frequencies in 1000 genetically unrelated voluntary blood donors from the same region of Brazil. The diagnosis of idiopathic chronic urticaria was based on the patients’ clinical histories and routine laboratory tests. Only the patients with positive ASSTs were selected. The allele distribution results from the patient and control groups were analyzed using odds ratios and 95% confidence intervals. RESULTS: No statistically significant differences were found between the ASST-positive patients with chronic urticaria and the control group, in relation to the MHC classes I and II alleles studied. CONCLUSIONS: We found that in this population group, there was no specific association between the HLA alleles studied (HLA-A, HLA-B and DRB1) and ASST-positive chronic urticaria. We believe that further population studies are needed in order to investigate the possible existence of this association.