BACKGROUND Neonatal lupus erythematosus (NLE) is a syndrome characterized by dermatitis and congenital heart block. The disease is mostly associated with transplacental passage of maternal anti-Ro(SS-A) or anti-La(SS-B) antibodies. Maternal HLA-DR3 and DQ2 alleles are associated with NLE in white and North American black populations. OBJECTIVE We sought evidence of a potential genetic disposition to NLE in mothers with a relatively homogeneous ethnic background. METHODS Class II human major histocompatibility complex HLA-DRB1, DQA1, DQB1, and DPB1 alleles were determined by polymerase chain reaction-restriction fragment length polymorphism in anti-Ro(SS-A)-positive mothers as well as in infants from seven Japanese families with siblings concordant or discordant for disease expression of NLE. RESULTS All seven mothers had two or three DQ alleles of DQA1 and DQB1 possessing specific amino acid residues, which are reportedly associated with anti-Ro(SS-A) autoantibody response in white and black populations. There was no class II HLA profile that distinguished disease manifestations of NLE in infants. CONCLUSIONS The HLA class II allele associations with anti-Ro(SS-A) autoantibodies that have been noted in other ethnic groups were also found in Japanese anti-Ro(SS-A)-positive mothers whose infants had NLE, suggesting shared susceptibility factors across racial barriers in maternal predisposition to Ro(SS-A) autoimmune response.