Severe combined immunodeficiency

Author: Brian Wu PhD. MD Candidate, Keck School of Medicine, Los Angeles, USA; Chief Editor: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, October 2015.

What is severe combined immunodeficiency?

Severe combined immunodeficiency (SCID) is considered to be the most serious of all primary immunodeficiencies. This rare congenital disorder is potentially fatal, due to severely compromised immune system marked by a combined absence of T-lymphocyte and B-lymphocyte function.

What causes severe combined immunodeficiency?

There are at least 13 different genetic defects associated with severe combined immunodeficiency. These defects interfere with the formation of lymphocytes. Around 70% of those with SCID are able to produce B-cells, but around 30% do not. In certain forms of this condition, the production of natural killer cells is also affected.

What are the risk factors for severe combined immunodeficiency?

There are risk factors of age, sex and ethnicity:

What are the signs and symptoms of immunodeficiency?

The signs and symptoms of immunodeficiency in SCID can vary, but do include:

How is severe combined immunodeficiency diagnosed?

The diagnosis severe combined immunodeficiency can be made from:

How is severe combined immunodeficiency treated?

The gold standard for SCID is a stem cell reconstitution from bone marrow transplant in the first 3 months of life, a procedure which has a 94% success rate. Immunoglobulin therapy is also common, as is gene therapy for X-linked ADA deficiency. ADA deficiency is sometimes also treated with injections of a modified form of ADA (an enzyme).

Treatment is critical. Without intervention, death will general occur by age 2.

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