(complement deficiency) A broad classification for rare genetic disorders with mostly autosomal recessive patterns of inheritance. They are caused by the ineffective or decreased biosynthesis of complement components. Complement deficiencies may also be acquired acutely post-infection or chronically from co-morbid autoimmune disorders. If complement components are adequately synthesized, their rapid depletion may result in functional deficiencies. Clinical signs of inherited deficiencies present within the first decade of life and are consistent with the signs of recurrent systemic infection or immune complex disease. Complement deficiencies decrease the effectiveness of the humoral immune response. Of all the complement deficiencies, C3 deficiency is associated with the poorest prognosis since it presents at an early age, when susceptibility to recurrent infection is great. Deficiencies of C3 and of the classical activating pathway components: C1, C4, C2 also predispose to immune complex disease.

(complement deficiency) A genetic deficiency of any component of the complement system, which may be associated with various pathologic conditions depending on the protein and activation pathway involved.

(complement deficiency) An immunodeficiency defined by the absent or suboptimal functioning of one of the complement system proteins.

(complement deficiency) Rare disease where complement protein(s) are absent or in diminished amount relative to the normal requirement of an organism; associated with autoimmune disease or increased susceptibility to infections, problems encountered depend on which pathway is affected.

The complement system is part of the innate immune system. The complement system plays an important part in defense against pyogenic organisms.