A clinical and serological comparison of familial and non-familial systemic lupus erythematosus in Ireland.

Seventeen families, in which the diagnosis of SLE could be verified in two relatives, were included in the study. The diagnosis was made according to the revised 1982 ARA criteria. We compared the 34 cases of familial SLE in these 17 families with 34 non-familial SLE controls matched for age, sex, ethnicity and duration of disease. Comparisons were made for the presence of 26 clinical and 11 serological features. The frequency of clinical features was similar between the groups. The frequency of anti-Ro antibody was higher in the non-familial group (15 out of 34 compared to 6 out of 34, P = 0.036, McNemar's test), although this was not significant after application of Bonferoni's correction for the number of comparisons. No cases of familial IgA or familial complement deficiency were identified. It was noted that 10 of the 34 non-familial patients and only one of the familial patients had the combination of anti-Ro antibody and photosensitivity. The findings of this study support the hypothesis that familial SLE and non-familial SLE are the same clinical entity, although there are differences in the subtypes of disease.