Complement factor 2 deficiency: a clinical and serological family study.

Inherited complement deficiencies are associated with a variety of connective tissue diseases. A family with inherited deficiency of complement factor 2 (C2) is described in which two family members with homozygous C2 deficiency developed cutaneous vasculitis and sicca syndrome. The other family members had heterozygous C2 deficiency and each member had the HLA-A25, B18, DR2 (w15) haplotype. The mother had seropositive rheumatoid arthritis. Further studies showed the presence of cryoglobulins, antibodies against endothelial cells, and anticardiolipin antibodies.