The genetic basis of alopecia areata: HLA associations with patchy alopecia areata versus alopecia totalis and alopecia universalis

Many diseases, notably those having a strong autoimmune component, have bee n shown to have an association with specific human leukocyte antigens (HLA) , The molecular basis for this genetic association with disease is the fact that HLA bind and present peptides derived from self and foreign protein a ntigens to the immune system for recognition and activation of the immune r esponse. Previous studies with heterogeneous groups of alopecia areata (AA) patients have suggested associations with some HLA class I and class II an tigens, For this study we selected only patients with long-standing disease and stratified them into two groups by strict definitions of duration and extent of disease: those with patchy AA and those with either alopecia tota lis (AT) or alopecia universalis (AU), The patients were tissue typed for H LA class II antigens by biomolecular methods that provided antigen discrimi nation at an allele level, More than 80% of all of the AA patients typed we re positive for the antigen DQB1*03 (DQ3), suggesting that this antigen is a marker for general susceptibility to AA, In addition, two other antigens were found significantly increased in frequency only in the group of AT/AU patients, DRB1*0401 (DR4) and DQB1*0301(DQ7). This strongly suggests that t he two clinical types of AA, namely patchy AA versus AT/AU, can be distingu ished by a genetically based predisposition to extent of disease.