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Severe Combined Immunodeficiency (SCID)

Also called: bubble boy disease, bubble baby disease

What is severe combined immunodeficiency (SCID)?

Severe combined immunodeficiency (SCID) is  a group of disorders that are passed down through families.  Infants born with SCID have defects in their immune cells. As a result, these children have problems fighting infections.

Three types of white blood cells, called T cells, B cells and NK cells, usually protect the body from invading viruses, bacteria and other invaders. T- and NK cells find and attack these invaders. B cells make antibodies that ward off infections.

In infants with SCID, the T-,  B and NK cells are missing or do not function correctly. Infants with SCID get infections easily because the immune system does not work correctly.

How common is SCID?

SCID occurs in about  one infant in every 50,000  live births. That means about 70 infants are found to have SCID in the United States each year.

What are the symptoms of SCID?

Symptoms of SCID in infants include the following:

  • Ear infections
  • Pneumonia or bronchitis
  • Oral thrush (a type of yeast that creates white, sore areas in the mouth)
  • Diarrhea that comes back or does not go away
  • Failure to  grow and gain weight as expected

What causes SCID?

SCID is caused by a change (mutation) in one or more genes that are involved in the immune system. Parents can be carriers of mutated genes that only cause problems when combined.

When one infant has SCID, parents should talk to a genetic counsellor about the chances of future children having with the same condition.

How is SCID diagnosed?

Newborn infants are screened for SCID at birth in hospitals across the United States. Screening is the most common way to find out whether infants have SCID. For infants who haven’t been screened, blood tests can be done to confirm SCID.

How is SCID treated?

Bone marrow transplant

The most effective treatment for SCID is bone marrow transplant (also known as a stem cell transplant). In this treatment, an infant with SCID receives healthy stem cells from a matched donor, usually a healthy brother or sister. The new cells then rebuild the immune system of an infant with SCID. It is possible for children who receive this type of transplant to be cured. Unfortunately, less than 25% of infants with SCID have this type of donor.

If no brother or sister is available for transplant, doctors may use stem cells from an unrelated donor or one of the parents. Patients who receive cells from a parent or an unrelated donor do not do as well as those with fully matched transplants. About a third of patients with partially matched donors develop immune system issues years afterward.

A bone marrow transplant has the best chance of working when it occurs in the first few months of an infant’s life. That is why an early SCID diagnosis is very important.

Gene therapy

St. Jude is leading research to provide better treatments for children with X-linked severe combined immunodeficiency disease (SCID-Xl). This is the most common type of SCID. It  almost always occurs in boys because the mutated gene is located on the X chromosome.

The St. Jude research study called LVXSCID-ND treats SCID-X1 with a new method called gene therapy. In this process, some of the patient’s bone marrow stem cells are removed and a corrected (normal) copy of the abnormal gene is placed into the infant’s own bone marrow stem cells. These cells are then transplanted into the patient’s body.

Learn more about our clinical trials for SCID and other diseases affecting the immune system.

Is there a cure for SCID?

For patients with a matched donor sibling, a bone marrow transplant can be curative. For patients without a matched donor sibling, a combination therapy developed at St. Jude may provide a cure. Results from a St. Jude clinical trial show that patients treated with gene therapy develop a healthy immune system.   

What are the survival rates for SCID?

Without treatment, infants with SCID usually die from infections within the first two years of life. With an early bone marrow transplant, frequent follow-up and prompt treatment for infections, survival rates are very good.

Why choose St. Jude for your child’s severe combined immunodeficiency treatment?

  • St. Jude has one of the leading gene therapy programs in the country and has expertise producing and using gene therapy vectors to treat blood and immune cell diseases.
  • A gene therapy developed at St. Jude has been shown to help patients develop a full complement of immune cells, that includes T cells, B cells and natural killer cells.
  • The St. Jude Bone Marrow Transplantation and Cellular Therapy Department is one of the largest pediatric programs of its kind in the world. We have performed more than 2,900 transplants since 1982.
  • The St. Jude Transplant Program is approved by the Children's Oncology Group (COG), the National Marrow Donor Program (NMDP), the Pediatric Blood and Marrow Transplant Consortium, and the Center for International Blood and Marrow Transplant Research (CIBMTR). The program is certified by the Foundation for Accreditation of Cellular Therapy (FACT).
  • St. Jude is part of the federally funded Primary Immune Deficiency Treatment Consortium, which aims to improve treatments for patients with SCID and other inherited immune disorders.
  • Doctors in the St. Jude Transplant Program work closely with scientists in the lab to quickly move new discoveries to patient care. The program conducts clinical trials to study these new discoveries.
  • St. Jude has experience performing transplants for SCID disorders. They also have an expert pediatric immunologist on staff who works closely with the transplant team.
  • The Transplant Unit at St. Jude is dedicated to the care of patients receiving bone marrow transplants, stem cell transplants or cellular therapy. The transplant team includes doctors and nurse practitioners with extensive training and experience in this lifesaving treatment for SCID. The team also includes registered nurses, a pharmacist, clinical dietitian, child life specialist and social worker.
  • The 18-bed Transplant Unit is staffed around the clock by nurses who are trained in the care of patients with SCID. The standard nurse-to-patient ratio is 2:1.
  • Each patient room in the St. Jude Transplant Unit has an adjoining parent room that includes a bed, bath, TV and phone, so parents can stay with their child throughout the transplant process.

Associated Clinical Trials

LVXSCID-ND: Gene Therapy for X-Linked Severe Combined Immunodeficiency (SCID-X1) in Newly Diagnosed Infants

A Pilot Feasibility Study of Gene Transfer For X-Linked Severe Combined Immunodeficiency (SCID-X1) in Newly Diagnosed Infants Using a Self-Inactivating Lentiviral Vector To Transduce Autologous CD34 + Hematopoietic Stem Cells

Diseases Treated:

X-linked Severe Combined Immunodeficiency (SCID-X1)


  • Diagnosis of Severe Combined Immunodeficiency, X-linked (SCID-X1)
  • Newborn to 2 years of age
  • No prior therapy with allogeneic stem cell transplantation
  • No HIV infection
View Trial