Conditions Severe Combined Immunodeficiency

Severe combined immunodeficiency (SCID) is an inherited condition in which the body is unable to fight off serious and life-threatening infections. Your body’s immune system is made up of different parts that work together to keep the body from getting sick. In a baby with SCID, certain parts of the immune system do not work properly. This puts the baby at risk of getting many infections. Children that do not get treatment for SCID rarely live past the age of two. However, when SCID is identified and treated before the baby gets infections, those children can live longer and healthier lives.

Condition Type

Other Disorders


Severe combined immunodeficiency (SCID) occurs in one out of every 40,000 - 75,000 births. SCID is more common in certain ethnic groups and geographic populations, including the Navajo and Apache populations in North America. There is also some evidence to suggest that it may be more common in people with Turkish ancestry.

Also known as

  • SCID
  • Bubble boy syndrome

Follow-Up Testing

Your baby’s doctor will ask you if your baby has any early signs of SCID (see Early Signs below). If your baby has certain signs, your baby’s doctor may refer you and your baby to a pediatric hospital for immediate treatment.

If your baby’s newborn screening result for severe combined immunodeficiency (SCID) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition.An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, a few babies do have the condition, so it is very important that you go to your follow-up appointment for a confirmatory test. Because babies with SCID may not be protected from life-threatening infections, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.

Follow-up testing will involve checking a sample of your baby’s blood to see if their immune system is working properly. Lymphocytes, a type of white blood cell, are an important part of the immune system. In babies with SCID, two types of lymphocytes are either not working well or not working at all: T-cell lymphocytes and B-cell lymphocytes.

For more information about SCID from the Immune Deficiency Foundation, check out this Parents Guide or Follow-Up Testing Guide.

About Severe Combined Immunodeficiency

Early Signs

Babies with severe combined immunodeficiency (SCID) are more likely to develop life-threatening infections. This is why early screening and identification are so important.

Early signs of SCID include:

  • High number of infections
  • Infections that do not improve with antibiotic treatment for two or more months
  • Diarrhea
  • Poor weight gain or growth (failure to thrive)
  • Thrush (a fungal infection) in the mouth or throat that does not go away

If your baby shows any of these signs, be sure to contact your baby’s doctor immediately



Your baby may need to stay away from young children. This makes it less likely they will catch an illness from another child.

Immunoglobulin Replacement Therapy

Babies with SCID should be placed on immunoglobulin replacement therapy if they are more than three months of age or have already had infections. Regular immunoglobulin replacement therapy can replace missing antibodies that help your baby fight infections.

Bone Marrow Transplant

The most effective treatment for SCID is a bone marrow transplant. Bone marrow makes cells for fighting infections and illnesses. In a bone marrow transplant, bone marrow cells from a person with a working immune system are given to a person with SCID, whose bone marrow cannot make cells to fight infections and illnesses.

Expected Outcomes

With early screening and treatment, babies with severe combined immunodeficiency (SCID) are less likely to develop life-threatening illnesses and infections. Children who receive bone marrow transplants often lead healthy lives.

If left untreated, babies with SCID can develop serious and fatal infections. Children with SCID who do not receive early treatment rarely live past two years of age.


Our immune systems are made up of special cells and proteins that protect us from germs and other things in our environment that can cause illnesses and infections. Specifically, T-cells and B-cells are types of white blood cells that are very important to our immune system.

If your baby has severe combined immunodeficiency (SCID), then their body either does not make enough or makes non-working T and B-cells. Without these working cells, the immune system cannot work correctly. This is why infants with SCID are more likely to catch serious infections and illnesses.

There are many different genetic causes of SCID. SCID may be inherited from parents or can be the result of a new genetic change in the child. All known forms of SCID follow either an autosomal recessive or an X-linked recessive pattern of inheritance.

When SCID is an autosomal recessive genetic condition, a child must inherit two copies of the non-working gene, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with SCID is rare, when both parents are carriers, they can have more than one child with the condition. Learn more about autosomal recessive inheritance.

When SCID is an X-linked recessive genetic condition, a male must inherit one copy of the non-working gene from his mother to have the condition. A female must inherit two copies of the non-working gene, one from each parent, in order to have the condition. In X-linked conditions, the gene is carried on the X sex chromosome; therefore, the condition affects males more than females. While having a child with SCID is rare, when one or both parents carry the non-working gene, they can have more than one child with the condition. Learn more about X-linked recessive inheritance.

Support for Severe Combined Immunodeficiency

Support Services

Support groups can help connect families who have a child or other family member affected with severe combined immunodeficiency with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates.

Accessing Care

Work with your baby’s doctor to determine the next steps for your baby’s care. Your baby’s doctor may help you coordinate care with a doctor who specializes in immunology or other medical resources in your community.

Because severe combine immunodeficiency (SCID) is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engineoffered by the American College of Medical Genetics and Genomics (ACMG) and the Find a Genetic Counselortool on the National Society of Genetic Counselors (NSGC) website are two good resources for you or your baby's health care provider to use to identify local specialists.

Families' Experiences

Cameron was diagnosed with SCID when he was four-months-old. Even though Cameron did not benefit from early diagnosis through newborn screening, he received prompt treatment after his diagnosis. A successful bone marrow transplant from his father has allowed him to lead a healthy life. Read Cameron’s story.

Scarlet was diagnosed with SCID when she was six-weeks-old. She received a successful bone marrow transplant and is now much healthier. Read her story.

For more information about SCID from the Immune Deficiency Foundation Advocacy Channel on Youtube, watch the video "SCID - A Family's Journey Through Isolation" below:

References & Sources

Visit the National Human Genome Research Institute for more information on SCID

Cossu F. Genetics of SCID. Ital J Pediatr. 2010 Nov; 36:76.

Li L, Moshous D, Zhou Y, et al. A Founder Mutation in Artemis, an SNM1-Like Protein, Causes SCID in Athabascan-Speaking Native Americans. J Immunol. 2002; 65(12): 6323-6329.

Shabestari MS, Maljaei SH, Baradaran R, et al. Distribution of Primary Immunodeficiency Diseases in the Turk Ethnic Group, Living in the Northwestern Iran. J Immunol. 2007; 27(5): 510-516.

ACT Sheets

Healthcare professionals can learn more about confirmatory testing by reading the American College of Medical Genetics and Genomics' Algorithm for Diagnosis and ACT Sheet, a guide for follow-up after newborn screening. You can visit this page of the ACMG website here.

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