HLA genotypes in a family with a case of homozygous C2 deficiency and discoid lupus erythematosus.

A fifty-year-old man with a history of recurrent bronchial and renal infections, and rheumatoid arthritis was admitted with a sunexposure-induced discoid lupus erythematosus. Complement levels and HLA typing of the patient and his family revealed a homozygous C2 deficiency in the patient and his HLA-identical healthy younger sister. The C2 deficiency gene was associated with HLA-A10, B18, DR2, C4A4B2, BfS on one chromosome and with HLA-A2, B7, DR2, C4A4B2, BfS on the other.