HLA-DRB1 and AIDS: The presence of DRB1*04 in subject I-1 (1st family) and DRB1*03 and DRB1*04 in subject II-2,4 (4th family) might be the reason for the occurrence of distinct AIDs within an individual (polyautoimmunity) and within members of a nuclear family (familial autoimmunity), supporting the concept of a shared autoimmune genetic background among AIDs.