What Is Severe Combined Immune Deficiency (SCID)?

SCID is an inherited condition that severely affects a baby's immune system.

The immune system fights infections and anything it sees as foreign invaders to the body.

Doctors label SCID as a "primary immunodeficiency" — a condition that keeps the immune system from working as it should.

Babies born with SCID don't have the immune cells they need to fight off infections. Because of this, they have a high risk of getting infections.

For kids with SCID, everyday illnesses become severe. Bacteria, viruses, fungi, and other germs not harmful to healthy children can be fatal to those with SCID.

How Common Is SCID?

It's extremely rare. SCID occurs in about one in 100,000 births.

Some types affect mostly males.

SCID may be more common (but still rare) in some Native Americans and people of Turkish descent.

What Causes SCID?

Children inherit the genes that cause SCID from their parents.

Changes in the IL2RG gene cause one type called X-linked SCID.

This gene tells your body how to make a protein needed for normal immune system function. Without it, the body has little to no immune response.

The IL2RG gene is on the X chromosome. Because males only have one X chromosome, one altered gene can cause SCID.

Females have two X chromosomes, meaning they need two copies of the faulty IL2RG gene to get SCID. This is why it mostly affects males.

The other type of SCID is due to an inherited broken gene for the enzyme adenosine deaminase. This is the enzyme your body needs to make T-cells, which attack viruses.

Changes in other genes cause other types of SCID.

SCID Symptoms

Babies are born with antibodies from their moms, which protect them from some illnesses. As these antibodies break down over the first few months, the baby's immune system kicks in.

This is when symptoms of SCID begin.

Symptoms of SCID are much like those of other childhood illnesses. But, SCID symptoms may last longer and become severe faster than symptoms of other diseases.

Symptoms of SCID may include:

  • Sinus, lung, and other respiratory infections keep coming back.
  • Ear infections.
  • Overgrowth of yeast in the mouth (thrush) or severe diaper rash.
  • Skin infections that don't respond well to treatment.
  • Diarrhea.
  • Slow growth or weight gain.

Complications of severe combined immunodeficiency

Children with primary immune deficiencies like SCID are more prone to infections than others. Their bodies may not clear these infections at all when treated.

This includes:

  • Pneumonia and bronchitis.
  • Meningitis.
  • Chickenpox.
  • Hepatitis (a liver infection).
  • Ear, sinus, and blood infections.
  • Diaper rashes and other skin rashes.

Infections that wouldn't have much effect on other children can quickly become life-threatening in kids with SCID.

You may need to isolate your child to protect them from germs.

Diagnosing SCID

Most states now screen newborns for this disorder because, although it's rare, it's vital to treat it early.

Doctors diagnose SCID by a blood test that measures lymphocytes — a type of white blood cell.

More blood tests can show what type of SCID disease is present and which immune cells aren't working as they should.

SCID Treatment

The goal of SCID treatment is to prevent your child from getting infections, which can become life-threatening.

Treating children with SCID can involve:

  • Treating infections as soon as they come up, usually with antibiotics.
  • Giving them extra antibodies through a transfusion.
  • Isolating them from others to avoid exposure to germs.

Enzyme-replacement drugs can treat some types of SCID, but not all kinds. This treatment doesn't cure SCID.

The most accepted treatment that cures SCID is a bone marrow transplant (BMT). Many children need to have this transplant before they're three months old.

The Hillman Center for Pediatric Transplantation pioneered a reduced-intensity BMT program. It helps reduce the adverse effects a bone marrow or stem cell transplant has on the body's organs.

Paul Szabolcs, MD

Chief, Blood and Marrow Transplantation and Cellular Therapies

Dr. Szabolcs is a pioneer in "reduced-intensity" chemo and transplants for children with rare immune disorders.

He can perform a lung transplant from the same donor, followed by a BMT. He's the first to show that this can help children with certain immune conditions.

Your Child's SCID Consult and Care: What to Expect

If a doctor diagnosed your child with severe combined immunodeficiency, we want you to know you're not alone. The Center for Rare Disease Therapy is here to help. 

Here's what you can expect when you come to us for your child's first SCID consult. 

What should I expect at my child's first visit for SCID care?

Your first visit to the center for your child's SCID exam will take four to six hours. Your child will receive a complete assessment from one of the center's doctors.

The doctor will make or confirm a SCID diagnosis and find out how much the disease has progressed.

Because we work as a team at the center, other doctors and staff might see your child during your visit.

These may include a:

  • Neurologist.
  • Heart doctor.
  • Surgeon.
  • Nutritionist.
  • Genetic counselor.
  • Psychologist.
  • Child development specialist.

What are the next steps after my child's SCID visit to the Center for Rare Disease Therapy?

Members of your child's SCID care team will talk with you about:

  • Likely next steps, such as tests or follow-up care.
  • Treatment options.
  • Ways to care for your child at home to help improve their quality of life.

If surgery might be an option for treating your child's SCID, we'll discuss all the details. We'll let you know how you and your child can prepare.

By the end of your visit, you'll have a SCID care plan tailored to your child's needs. We'll also schedule a follow-up visit in three months.

You'll meet our nurse practitioner, who can answer your questions by phone or video conference any time before your next visit.

Before you leave, please ask us about your child's SCID diagnosis, treatment, or anything else on your mind.

How long will I wait for my child's SCID test results?

We'll call within two weeks to review the test results and the next steps for your child's SCID care.

You can also find your child's test results if you have a MyCHP — Children's patient portal account. It's free for patients, parents, and guardians of UPMC Children's Hospital of Pittsburgh.

Partners in Your Child's SCID Care

A child with a rare disease like severe combined immunodeficiency syndrome affects the whole family.

At the Center for Rare Disease Therapy, we see each family member as our partner.

The best care approach happens when we merge our SCID expertise with your knowledge of your child's needs. 

Center for Rare Disease Therapy patient storiesMeet Our Patients

Learn how our Center for Rare Disease Therapy experts help children with SCID and their loved ones.

View Center for Rare Disease Therapy patient stories. »

Contact Us

At the Center for Rare Disease Therapy, every child diagnosed with a rare disease receives an individualized treatment plan and family-centered care.

For an appointment, consultation, or patient referral with an expert at UPMC Children’s Hospital of Pittsburgh, please fill out our contact form and we will be in touch within two business days.

Phone: 412-692-7273
Email: RareCare@chp.edu