Severe combined immunodeficiency disease

Severe combined immunodeficiency disease (SCID) is a rare, genetic disorder characterized by a severely compromised immune system. Individuals with SCID are highly susceptible to infections and often experience severe, recurrent infections that can be life-threatening. SCID is considered a form of primary immunodeficiency.

Causes

SCID is caused by genetic mutations that affect the development and function of T cells and B cells, which are critical components of the adaptive immune system. The most common form of SCID is X-linked SCID, which is caused by mutations in the IL2RG gene. Other forms of SCID can result from mutations in genes such as ADA, RAG1, and RAG2.

Symptoms

Symptoms of SCID typically appear in infancy and include severe infections, failure to thrive, and chronic diarrhea. Infants with SCID may also develop autoimmune diseases and are at risk for graft-versus-host disease if they receive blood transfusions or bone marrow transplants from non-matched donors.

Diagnosis

SCID can be diagnosed through genetic testing and newborn screening. Early diagnosis is crucial for effective treatment. Newborn screening for SCID involves testing for low levels of T-cell receptor excision circles (TRECs), which are byproducts of T-cell development.

Treatment

The primary treatment for SCID is a bone marrow transplant, which can restore the immune system by providing the patient with healthy stem cells. Gene therapy is an emerging treatment option that involves correcting the genetic defect in the patient's own stem cells. Supportive treatments include antibiotics, antiviral drugs, and immunoglobulin therapy to prevent and manage infections.

Prognosis

The prognosis for individuals with SCID has improved significantly with early diagnosis and treatment. With a successful bone marrow transplant or gene therapy, many patients can achieve a functioning immune system and lead relatively normal lives. However, without treatment, SCID is typically fatal within the first year of life.

Related Pages

• Primary immunodeficiency
• Bone marrow transplant
• Gene therapy
• Autoimmune disease
• Graft-versus-host disease

See Also

• Immunology
• Genetic testing
• Newborn screening