complement abnormality, an unusual condition characterized by deficiencies or dysfunctions of any of the 11 serum proteins known as complement and designated C1-C11. The most common abnormalities are C2 and C3 deficiencies and C5 familial dysfunction. Patients with complement abnormalities may be more susceptible to infections and to collagen vascular diseases. Primary complement abnormalities may be inherited, whereas secondary complement abnormalities may stem from immunological reactions, such as drug-induced serum disease, which depletes complement. Complement deficiencies may be associated with other illnesses, such as acute streptococcal glomerulonephritis, acute systemic lupus erythematosus, and dermatomyositis. ▪ OBSERVATIONS: Increased susceptibility to systemic bacterial infection is associated with C2 and C3 deficiencies and with C5 familial dysfunction. Chronic renal failure and lupus erythematosus may also be associated with C2 deficiency. Signs of C5 dysfunction are malaise, diarrhea, and seborrheic dermatitis. Diagnosis of complement abnormalities is difficult and often expensive. Some indications are electrocardiographic conduction abnormalities; detection of complement and immunoglobulins in the walls of blood vessels in glomerulonephritis; cerebrospinal fluid pleocytosis; increased erythrocyte sedimentation rate; and presence in the urine of red blood cells (RBCs), RBC casts, and protein. ▪ INTERVENTIONS: Replacement of complement-fixing antibodies and control of infection and associated illnesses are part of standard treatment for complement abnormalities. The patient commonly receives transfusion of fresh plasma to replace antibodies. Bone marrow transplantations and injection of gamma globulin may also be used, but the former carries the risk of a fatal graft-versus-host reaction. Complement abnormalities are usually corrected temporarily by replacement therapy, but no permanent cure is available. ▪ PATIENT CARE CONSIDERATIONS: Patients should be carefully monitored, especially if they are receiving gamma globulin injections. Patients also should be instructed to exercise scrupulous hygiene, to seek prompt treatment of even the smallest wounds, and to avoid crowds or persons with active infections. Members of the health care team should be alert for early signs of ataxia or slight changes in mental activity that may signal neurological damage caused by infection.
