Familial systemic lupus erythematosus in Finland

OBJECTIVE: To perform a cross sectional nation-wide clinical study of familial systemic lupus erythematosus (SLE) in Finland. METHODS: We sought to identify all Finnish families in which at least 2 members satisfied the classification criteria for SLE. About 1,200 patients with SLE (80-85% of all patients attending Finnish hospitals) were contacted. Personal and/or phone interviews and examination of medical records were used to verify the diagnoses. A comparison of clinical characteristics was made between familial cases of SLE and matched sporadic controls. RESULTS: We identified 53 multiplex families with 113 SLE patients. Forty-six families had 2 affected members and 7 families had 3 affected members. There were 3 pairs of monozygotic female twins and one pair of dizygotic twins of the opposite sex concordant for SLE. Eleven (9.7%) of the 113 familial cases of SLE were male. No differences were found in the clinical presentation of SLE between familial and sporadic cases (sex, age at onset, major clinical manifestations, and common laboratory tests). The incidence of familial SLE was approximately 4-5%. CONCLUSION: Our study shows that familial and sporadic SLE are not different disease entities; this means that we can extrapolate the results of future genetic analyses in multiplex SLE families to all patients with SLE.