Since a deletion of the C4A and CyP21A genes is reported to account for C4AQO in patients with systemic lupus erythematosus (SLE) in Caucasians, we studied the restriction fragment length polymorphism (RFLP) of genomic DNA to determine whether similar deletions of the C4A and CyP21A genes occur in Japanese patients with SS.
We conclude that a large C4A,CYP21A gene deletion, particularly associated with the HLA-B44, -DR2, and -DR3 alleles, is the strongest genetic risk factor thus far identified for SLE susceptibility in black Americans.