With regard to DM, Scott described elevated C3d levels in six out of seven patients with active juvenile DM (Scott and Arroyave, 1987); Campo and colleagues observed a correlation between serum levels of C3a and, to a lesser extent, C5b-9 with disease activity in 16 patients with DM (Campo et al., 2007); elevated serum C5b-9 levels and higher deposition of activated C3 fragments on red cells (as measured by an in vitro C3 uptake assay) were reported in a cohort of 13 DM patients, which normalized after treatment with intravenous immunoglobulins (Basta and Dalakas, 1994). This evidence concerns the gene C3 and dermatomyositis.