Objectives To evaluate the frequency of autoimmune disorders in Icelandic multicase SLE families.

Methods The study group consisted of 38 SLE patients, 127 first-degree relatives, 37 s-degree relatives and 33 nonconsangineous relatives from multicase SLE families. Pedigree members were evaluated through interviews and physical examination, medical records were reviewed. A standardised protocol for SLE and other autoimmune disorders was used. Serum samples were obtained and autoantibodies measured.

Results Among the SLE patients, 16/38 (42%) had other autoimmune disorder (s) (11 Sjogrens syndrome/sicca symptoms, 3 interstitial cystitis, 3 psoriasis, 3 pernicious anaemia, 3 thyroid disease, 2 myositis). Twenty six/164 (16%) first- and second-degree relatives had various autoimmune disorder (s) (14 Sjogrens syndrome/sicca symptoms, 8 thyroid disease, 6 RA, 3 psoriasis, 3 alopecia, 3 iritis, 1 pernicious anaemia, 1 PBC, 1 MS, 1 DM, 1 AS, 1 reactive athritis, 1 discoid LE). Additionally, 21/164 (13%) relatives had autoantibodies. Therefore either autoimmune disorder (s) or autoantibodies were present in 29% of the relatives. Two of 33 (6%) nonconsangineous relatives had autoimmune disorders and 6/33 (18%) had autoantibodies.

Conclusion Autoimmune disorders in general are present in increased frequency in these Icelandic multicase SLE families.