Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (831 page)

   Pseudogout and gout

   Reiter syndrome

   Gonococcal arthritis

Decreased in Inherited Conditions (see Complement Components in Plasma and Their Deficiencies table)

Inherited deficiencies are characterized by the absence of single complement component.
Most inherited disorders of the classical pathway are transmitted as autosomal recessive traits and are symptomatic in the heterozygous. Exception is partial C4 deficiency that predisposes to SLE.

   Hereditary angioedema an autosomal dominant disease; patients have very low C4, but normal C3

   C1q deficiency: more than 90% develop SLE

   Deficiency of C1r or C1s as well as partial deficiency of C4 predispose to the development of SLE

   Deficiency of C4a or C4b is associated with the development of other diseases (scleroderma, IgA nephropathy, childhood diabetes, etc.)

   Familial Mediterranean fever (C5a inhibitor)

   Urticarial vasculitis and recurrent infections (C3)

   Severe combined immunodeficiency (C1q)

   X-linked hypogammaglobulinemia (C1q)

   Recurrent neisserial infections (C5, C6, C7, C8, C9, and the alternate pathway)

   Congenital deficiencies of C2 or C4 may present with lupus-like or other autoimmune disorder involving: