MOLECULAR HETEROGENEITY OF C2 DEFICIENCY

The most common of the complement deficiencies in populations of European origin is a genetic deficiency of the second component of complement (C2).1 Rheumatologic disorders such as systemic lupus erythematosus, Henoch—Schönlein purpura, and polymyositis have been recognized in more than half the patients with this deficiency. To a lesser extent, C2 deficiency has been associated with increased susceptibility to infection.2 Genes encoding the proteins C2 and C4 (the fourth component of complement) of the classic complement-activation pathway and factor B of the alternative pathway are located in the major histocompatibility complex (MHC) on the short arm of chromosome 6 between. © 1992, Massachusetts Medical Society. All rights reserved.