Complement Deficiencies

Definition

Complement deficiencies are a group of disorders in which there is a reduced level of specific proteins, complement, involved in proper immune functioning.

Description

Complement plays several functions in immunity. It can poke holes in bacteria, kill bacteria that are first targeted by antibodies, or, working with antibodies, point out which bacteria need to be engulfed by white blood cells. Without sufficient complement, the body is prone to frequent infections, like pneumonia or meningitis, or other illnesses, including autoimmune diseases, like systemic lupus erythematosus. Since there are more than 20 different types of complement, the disease that results depends on the specific complement that is lacking.

Cause and symptoms

A defect in the complement system can be genetic, but a secondary complement deficiency can also result from ailments that involve a lot of protein loss, including serious burns, liver or kidney disease, and autoimmune diseases, like lupus. Symptoms vary depending on the specific complement deficiency and the disease that results. Some people remain healthy with no symptoms at all. Others, who suffer from frequent infections, may develop a high fever, diarrhea, headaches with a stiff neck, or a cough with chest pain. If an autoimmune disease develops, like lupus, the person may lose weight, suffer from a rash, and have joint pain. Other symptoms of complement deficiency diseases (like hereditary angioedema, paroxysmal nocturnal hemoglobinuria, or leukocyte adhesion deficiency syndrome) include abdominal and back pain, skin infections, edema or swelling of the face and red bumps on the skin.

Diagnosis

There are blood tests which determine the activity of the complement system. The two most common screening tests, CH50 and APH50, tell the physician which group of complement components have a defect. More specific blood tests for the individual complement components (e.g., C3 or C4 complement) are then performed. Other specialized blood tests, including C1 esterase level, Ham test, and a white blood count, may also be performed.

Treatment

There is no way to treat the actual complement deficiency. However, antibiotics are used to treat infections and vaccinations are given to reduce the risk of disease. Often, the person is vaccinated against infections that include influenza, pneumonia, and meningitis. In some cases, (e.g. a specific disease called paroxysmal nocturnal hemoglobinuria [NH]) a bone marrow transplant may be recommended.

Alternative treatment

There is no alternative treatment for complement problems.

Prognosis

Since complement deficiencies include a wide range of disorders, the prognoses can also vary widely. Some patients remain healthy their entire life. Others are hospitalized frequently because of infections which, if not properly treated, can be fatal. Those with autoimmune diseases could have a normal life expectancy. There are some complement deficiencies, that have a high mortality rate. In those cases, death may occur within 10 years after diagnosis.

Prevention

There is currently no way to prevent complement deficiencies.

Resources

ORGANIZATIONS

Immune Deficiency Foundation. 25 W. Chesapeake Ave., Suite 206, Towson, MD 21204. (800) 296-4433. 〈http://www.primaryimmune.org〉.

OTHER

"The Clinical Presentation of the Primary Immunodeficiency Diseases." International Patient Organization for Patients with Primary Immunodeficiences. 〈http://www.ipopi.org〉.

KEY TERMS

Autoimmune diseases— A group of diseases, like rheumatoid arthritis and systemic lupus erythematosus, in which immune cells turn on the body, attacking various tissues and organs.

Hereditary angioedema— A complement deficiency characterized by lymphatic vessel blockages that cause temporary swelling (edema) of areas of the skin, mucous membranes, and, sometimes, internal organs.

Leukocyte adhesion deficiency syndrome— A complement deficiency syndrome characterized by recurrent infections of the skin, mucous membranes, and gastrointestinal tract and the absence of pus formation. This disorder is sometimes apparent at birth when separation of the umbilical cord takes longer than normal.

Meningitis— An inflammation of the lining surrounding the brain and spinal cord.

Paroxysmal nocturnal hemoglobinuria (PNH)— A rare complement disorder characterized by episodes of red blood cell destruction (hemolysis) and blood in the urine (hemoglobinuria) that is worse at night.

Systemic lupus erythematosus— An autoimmune disease in which the immune system attacks the body's connective tissue. A butterfly-shaped facial rash is characteristic.

White blood cells— Cells that are key in immune defense. There are various types, including those that engulf and kill invading bacteria.