What is the prognosis of severe combined immunodeficiency (SCID)?

Updated: Apr 28, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD  more...
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Without treatment, death from infection usually occurs within the first 2 years of life. Diagnosis must be made before severe life-threatening infections occur so that the immunity can be restored with enzyme replacement or BMT; such treatment can lead to long-term survival. With bone marrow and other stem cell reconstitution techniques, many patients with SCID are fully reconstituted without complications.

GVHD from maternal cell engraftment can occur in any SCID case. The transfusion of nonirradiated blood products is an important cause of GVHD in all forms of SCID. The risk for GVHD or graft failure has declined significantly with newer techniques that include T-cell depletion using monoclonal antibodies and, possibly, the use of cord blood CD34+ stem cells. In selected patients with SCID, pretransplant immunosuppression is not necessary.

Patients who are well-nourished, uninfected, and younger than 6 months before transplantation have the best outcomes. Allogeneic hematopoietic stem cell transplantation (HSCT) in patients younger than 3-4 months of age is associated with better outcomes.

Patients with common γ chain (XL-SCID) or JAK3 mutations have an increased risk of hypogammaglobulinemia after transplantation because of the retention of recipient B cells that do not respond adequately to donor T-cell communication.

Although patients with SCID rarely survive without stem cell reconstitution, gene therapy may be a viable alternative for XL-SCID and ADA deficiency in patients who are unable to find donors if the complication of acute lymphoblastic leukemia is effectively prevented.

Patients with less severe ADA mutations have survived into adulthood. An optional treatment for ADA deficiency is polyethylene glycol (PEG)-treated ADA replacement, although this does not return immune function to normal.

Cartilage-hair hypoplasia, particularly in the Finnish population, may be less severe.

Early infancy is characterized by recurrent failure to thrive and a number of common infections, including otitis media, diarrhea, and opportunistic infections such as mucocutaneous candidiasis and CMV infection. If SCID is not recognized by age 6 months, opportunistic infections become more evident, especially P jiroveci pneumonia and invasive fungal infections. Common childhood viral illnesses may prove fatal in SCID. These include infections with VZV, RSV, rotavirus, parainfluenza virus, CMV, Epstein-Barr virus (EBV), enterovirus, and adenovirus.

In classic cases, vaccination with the attenuated oral polio strain causes disseminated infection and resultant death.

Some patients with cartilage-hair hypoplasia, ADA deficiency, MHC class II, or a less severe mutation in XL-SCID survive longer. The former variant is associated with a high incidence of non-Hodgkin lymphoma.

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