Severe Combined Immunodeficiency (SCID)

On December 1, 2012, the Texas Department of State Health Services (DSHS) began screening for Severe Combined Immunodeficiency (SCID). SCID is a group of genetic disorders characterized by profound defects in the immune system, the body’s line of defense against all types of infections. SCID is one of the most serious and life-threatening forms of immune system problems. It occurs in about one in 40,000 to one in 100,000 newborns. Although rare, SCID can be successfully treated if identified early in life. If not treated, most of the affected infants die within the first year of life. SCID will be detected using the same newborn screen specimen collected from a heel stick and tested at the Texas Department of State Health Services Laboratory.

Things To Know About SCID

What is SCID

SCID is a rare, serious group of disorders involving the immune system. The immune system is composed of T and B lymphocytes (T and B cells), the white blood cells responsible for fighting infections caused by viruses, bacteria and fungi. Babies with SCID are not able to fight infection. They appear healthy at birth but can become sick very quickly when exposed to common illnesses. SCID is so rare that medical providers might not diagnose it until it is too late to provide lifesaving treatment.

What Causes SCID

SCID is a disorder caused by changes in genes involved in immune function that are passed on (inherited) from parents to child. One or both parents of an affected child carry a gene change that can cause SCID. Parents usually do not have signs or symptoms, or even know they carry the gene change.

There are several different forms of SCID. An altered gene, passed to the baby from one or both parents, is associated with many forms of SCID. However, sometimes the SCID gene shows up for the first time in the newborn without being passed down from a parent (spontaneous occurrence). In most instances of infants born with SCID there are no other known cases of SCID in the family. Unless there has already been a baby born with SCID in the family, there is no way for a couple to know who is at risk of carrying a gene that causes SCID. 

Testing for SCID

All Texas newborns get two blood tests that screen for 55 congenital disorders and point-of-service screenings for hearing and critical congenital heart disease. 

Newborn screening will detect most but not all cases of SCID.

An abnormal newborn screen for SCID does not mean the baby has SCID, but it does mean the baby needs more testing to know for sure. Your baby’s doctor will be notified by the newborn screening program to arrange for additional testing. If your child shows symptoms of SCID, they should be evaluated by a specialist.

Doctors (pediatric immunologists) working in centers that specialize in treating disorders of the immune system can help with the diagnosis.

• They check the baby’s immune system.
• They take a family medical history, perform a physical exam and obtain any necessary blood tests. 
• A family history of SCID may alert the doctors to a diagnosis before the baby develops symptoms.
• However, babies may have SCID even if no one in their family has had SCID.

Things to Remember

Prompt treatment can improve a child’s length and quality of life. It is very important for you to receive instructions from your doctor regarding follow-up testing and treatment.

• Blood test results can show if the baby’s immune system is not working properly.
• Early diagnosis is important because the treatment is most effective within the first three months of life.
• Newborns with SCID can have a healthy immune system if they get care very early in life.
• When there is no family history of SCID, children are often not diagnosed until six months of age, or older if they have not had a newborn screen that includes SCID.

Treatments

SCID can be treated. The most common treatment is hematopoietic stem cell transplantation (HSCT) most often, bone marrow transplantation. Other forms of SCID may be treated with enzyme replacement therapy. Some babies who have a HSCT might still need additional lifelong treatment.

Without proper treatment many babies with SCID die. However, with a newborn screening test for SCID, earlier diagnosis may be possible.

• To stop infections in children with SCID, doctors may prescribe antibiotics and advise keeping the child away from sick people and crowds.
• They may also give special treatments to help children fight infection.
• Infants suspected of having SCID should not be given the LIVE ATTENUATED ROTAVIRUS VACCINES, or any other live vaccine until the immunologist has approved the vaccine.
• A bone marrow transplant is the best treatment for SCID. A transplant is usually done using the bone marrow of a sibling of the child with SCID, although a parent’s bone marrow might also be used. Some children may not have family members who are able to donate bone marrow. Doctors may be able to use bone marrow from a non-related donor.
• Some types of SCID are caused by an enzyme not functioning properly. In these cases, weekly injections of the enzyme may be given. However, this is not a cure and children must receive the injections for the rest of their lives.
• In some instances, depending on the altered gene that caused SCID in your baby, other treatments are possible and immunology specialists will discuss these with you.
• All these treatment options need to be done in a specialized medical center where there are doctors called pediatric immunologists who are experienced with SCID. 

Genetic Counseling

Since there are multiple genes that may be involved with SCID, genetic counseling is recommended for every family whose infant has been diagnosed with SCID. One of the more common forms of SCID affects boys while other forms affect boys and girls. If the genetic problem causing SCID is found through testing and/or family history, then it may also be possible to test a baby before birth, which can lead to early treatment.

Additional Information

• March of Dimes
• Immune Deficiency Foundation
• American College of Medical Genetics and Genomics                             
• American Academy of Pediatrics
• Genetics Home Reference

Call the Texas Department of State Health Services and speak with a nurse at 1-800-252-8023, ext. 3957. 

Last updated March 8, 2021