Human leukocyte antigen region involvement in the genetic predisposition to alopecia areata.

Human leukocyte antigens (HLA) of classes I and II were studied in 127 patients with alopecia areata (AA). The patients were subdivided into different groups depending on (1) hair loss area, (2) sex, (3) pathogenesis, (4) response to topical immune modulators (squaric acid dibutylester and diphencyprone) and (5) age of onset of the disease. The frequencies of class I HLA markers (loci A, B, C) were not significantly different from the controls. However, among the class II antigens (loci DR, DQ), the frequency of DR5 was increased in both alopecia areata and alopecia universalis when compared with the control group. In particular, DR5 was strongly linked to the early-onset form. The highest DR5 frequency (62%) was found in the group of patients which presented both the early onset and the most severe form of the disease (p