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Leukocyte adhesion deficiency syndrome

Leukocyte adhesion deficiency, abbreviated LAD, is a rare autosomal recessive disorder characterized by immunodeficiency resulting in recurrent infections. The disorder is often divided into two separate genotypes called type I and type II, with type II being associated with fewer infections but more developmental delay. more...

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Epidemiology

LAD is a rare disease; its estimated prevalence is 1 in 100,000 births. There is no described racial or ethnic predilection.

Clinical manifestations

LAD was first recognized as a distinct clinical entity in the 1970s. The classic descriptions of LAD included recurrent bacterial infections, defects in neutrophil adhesion, and a delay in umbilical cord sloughing. The defects in adhesion result in poor neutrophil chemotaxis and phagocytosis.

Patients with LAD suffer from bacterial infections beginning in the neonatal period. Infections such as omphalitis, pneumonia, gingivitis, abcesses, and peritonitis are common and often life-threatening due to the infant's inability to properly destroy the invading pathogens.

Molecular defect

The inherited molecular defect in patients with LAD is a deficiency of the beta-2 integrin subunit of the leukocyte cell adhesion molecule, which is found on chromosome 21. This subunit is involved in making three other proteins (LFA-1, CR3, and Mac-1) This basically means that a gene which creates a protein does not function properly. This results in the lack of important molecules which help neutrophils make their way from the blood stream into the infected areas of the body (ie the lungs in pneumonia). Those neutrophils which do manage to make it to the infected areas have a difficult time "swallowing" the bacteria leading to infection (this is known as impaired phagocytosis). Therefore, the infection is allowed to spread unimpeded and cause serious injury to important tissue.

Diagnosis

Typically diagnosis is made after several preliminary tests of immune function are made, including basic evaluation of the humoral immune system and the cell-mediated immune system. Specific diagnosis is made through monoclonal antibody testing for CR3, one of the three complete proteins which fail to form properly as a result of beta-2 integrin subunit deficiency.

Treatment

Once the diagnosis of LAD is made, bone marrow transplantation is the current standard of care. However, some progress has been made in gene therapy, an active area of research.

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Complement deficiencies
From Gale Encyclopedia of Medicine, 4/6/01 by Jeanine Barone

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 & 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, as well as 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 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, 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 (PNH), 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, e.g. PNH, which 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.

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.
Leucocyte 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 which engulf and kill invading bacteria.

Further Reading

For Your Information

    Books

  • McLean, Robert H and Thomas R. Welch. "Complement." In Handbook of Human Immunology, edited by Mary S. Leffell, et al. Boca Raton: CRC Press, 1997.

    Periodicals

  • "Complement Deficiency States." Immune Deficiency and Allied Disorders Newsletter 2(June 1996): 1-6.

    Organizations

  • Immune Deficiency Foundation. 25 W. Chesapeake Avenue, Suite 206, Towson, MD 21204. (800)296-4433.

    Other

  • Immune Deficiency Foundation. "The Clinical Presentation of the Primary Immunodeficiency Diseases." http://ipopi.org/idt/clinpres.html.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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