Association between ABO blood groups, HL-A antigens and periodontal diseases in young adults: a follow-up study.

Two hundred and thirty-eight Caucasians were studied for ABO blood typing and for HL-A antigens. The subjects were divided into normal, necrotizing ulcerative gingivitis, chronic gingivitis, periodontosis and periodontitis groups. Results showed the chronic gingivitis group was significantly different in ABO grouping than the control group with the gingivitis subjects having a larger percentage of AB types and a smaller percentage of O types. The periodontosis group showed a trend toward more A and B blood groups and a smaller percentage of O groups than the controls. Compared to the normal group there was a significant reduction in HL-A2 antigen frequency in the periodontitis groups and a trend in reduced frequency in the periodontosis group.