Complement levels in dogs with familial canine dermatomyositis.

CH50, C4, C2, and C3 levels were evaluated in 7 dogs affected with dermatomyositis and in 22 control dogs. Dogs with dermatomyositis did not have clinical evidence of active disease at the time of serum collection for complement assays. No absolute complement component deficiency was identified in dermatomyositis-affected dogs in this study; however, a statistical difference in C2 was identified between control dogs of non-collie breeds and control collies, suggesting there may be a breed difference in complement levels.