Age has been suggested to modify systemic lupus erythematosus expression. In this study we have attempted to study 13 patients with late onset (40 years and above) and 90 with early onset disease (below 40 years) to determine whether age-related differences in disease expression exist and whether the genetic make-up influences the age of disease onset. We found that patients with late onset disease initially presented with pericarditis (31% vs 3%, P<0.005) and a lower incidence of malar rash (31% vs 57%, p<0.05). During the disease course, there was a lower incidence of mucocutaneous symptoms especially malar rash (p<0.005) and psychosis (p<0.05) in the late onset group. Serological parameters were similar in both groups. There was a prevalence of HLA-DQA1*0103 in Chinese patients with late onset disease (pcorr=0.004). These findings suggest that a subgroup of late onset patients may experience milder disease and that the risk conferred by the HLA-DQA1*0103 may be significant among these patients.