Complement Deficiency

Complement deficiency is an immunodeficiency caused by the absence or reduced function of one of the proteins of the complement system, a part of the immune system that helps clear pathogens and damaged cells. Because other parts of the immune system can partly compensate, many cases go undetected, with some studies estimating that fewer than ten percent are ever diagnosed; a broader drop in complement activity from any cause is called hypocomplementemia, while a decline linked to another underlying illness rather than an inherited defect is called secondary complement disorder. The condition can be inherited or acquired, and typically presents as recurring infections or rheumatic disease, diagnosed through blood tests measuring total complement activity, and managed in some cases with immunosuppressive therapy.