Severe Combined Immunodeficiency

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Severe Combined Immunodeficiency is not the name you expected.

Disorder Subdivisions

  • None

General Discussion

Severe combined immunodeficiency (SCID) is a group of rare congenital syndromes with little or no immune responses. This results in frequent recurring infections with bacteria, fungi, and viruses. Infections that are minor in most people can be life‑threatening in people with SCID.

The immune system includes specialized white blood cells that work together to fight off bacteria, fungi, and viruses. These white blood cells include T lymphocytes (T cells) that are central mediators of the immune response and also directly attack viruses. B lymphocytes (B cells) produce antibodies that attach to invaders and mark them to be destroyed, but they need T cells to work effectively. Natural killer (NK) cells are specialized to help fight viruses as well. Patients with SCID have a genetic defect that affects T cells and at least one other type of immune cell (hence "combined immunodeficiency").

Types of SCID are classified by which immune cells, T, B, and/or NK cells, are defective. There are several types of SCID, each caused by a different genetic (hereditary) defect. Despite the type of SCID, the primary symptom is reduced or absent immune function and all forms of classic SCID are lethal unless treated appropriately. The type of SCID helps determine the best treatment.

Most states now have newborn screening for SCID to help detect and treat babies prior to them becoming sick. Early detection by newborn screening has dramatically increased the success of the bone marrow transplantation as babies with SCID can avoid early infections.

Supporting Organizations

European Society for Immunodeficiencies

1-3 rue de Chantepoulet
Geneva, CH 1211
Tel: 410229080484
Fax: 41229069140

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311

Immune Deficiency Foundation

110 West Road
Suite 300
Towson, MD 21204
Tel: (410)321-6647
Fax: (410)321-9165
Tel: (800)296-4433

International Patient Organization for Primary Immunodeficiencies

Firside Main Road
Cornwall, PL11 3LE
United Kingdom
Tel: 441503250668
Fax: 441503250961

Rare Diseases Clinical Research Network

University of South Florida, Pediatrics Epidemiology Center
3650 Spectrum Boulevard, Suite 100
Tampa, FL 33612
Tel: (813)396-9501
Fax: (813)910-5997
Tel: (866)533-9104

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). For a full-text version of this report, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report.

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

Last Updated:  2/26/2016
Copyright  2016 National Organization for Rare Disorders, Inc.