Adenosine Deaminase Deficiency: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Adenosine Deaminase Deficiency?
An immunologist (a doctor who treats immune system problems) usually leads the care. Treatment is done at a transplant center that explains the options and risks. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is adenosine deaminase deficiency?
Adenosine deaminase (ADA) deficiency is a rare inherited disorder that affects the immune system. The immune system protects the body from bacteria, viruses, and fungi. It harms the development and work of lymphocytes, white blood cells that help the body fight infections. About 80 percent of people with ADA deficiency also have severe combined immunodeficiency (SCID). With SCID, the body has almost no immune protection. It is very rare and occurs in about 1 in 500,000 newborns worldwide.
Symptoms
Babies with ADA-SCID usually have health problems within the first 6 months of life. Signs can include:
- Pneumonia and other serious infections that keep coming back. Germs that rarely make healthy people sick can cause life-threatening illness.
- Chronic diarrhea, meaning loose stools that last.
- Widespread skin rashes.
- Slow growth and trouble gaining weight.
- Developmental delays, meaning learning to walk or talk later than usual.
Without treatment, babies with ADA-SCID usually do not survive past age 2. About 15 to 20 percent of people have a milder form with later onset, called ADA-CID. It often causes repeated upper respiratory infections (infections of the nose and sinuses) and ear infections. Over time it can lead to chronic lung damage and malnutrition (not getting enough nutrients). Some people have partial ADA deficiency. It only affects red blood cells, so their immune system works normally and they have no health problems from it.
Causes and who gets it
ADA deficiency comes from changes (variants) in the ADA gene. This gene gives the body instructions for making the enzyme adenosine deaminase. The enzyme gets rid of deoxyadenosine, a molecule made when DNA breaks down. Too much of it kills young lymphocytes in the thymus (a gland behind the breastbone) before they can mature. Without enough working enzyme, the body has too few lymphocytes to fight infection. In general, the less working enzyme a person has, the more severe the condition. The condition is inherited in an autosomal recessive pattern. That means both copies of the ADA gene must be changed. About 15 percent of people with SCID have ADA deficiency.
How doctors diagnose it
Most states use newborn screening to find SCID early. The screen uses a dried blood spot from the newborn screening card. It measures T-cell receptor excision circles (TRECs). A low result means the baby has low numbers of lymphocytes (white blood cells that help the body fight infections) in the blood. Doctors confirm the result with more tests. A complete blood count is a blood test that counts the blood cells. Lymphocyte subset testing counts the different kinds of lymphocytes. Together they may show low levels of B, T, and/or NK cells. Doctors also check how well the ADA enzyme works, especially when newborn screening misses the milder form.
Treatment
Treatment has two main options. Enzyme replacement therapy injects the missing enzyme on a regular schedule. It is a treatment, not a cure. One form, Revcovi (elapegademase-lvlr), was approved in 2018 for children and adults with ADA-SCID. A stem cell transplant takes stem cells (blood-forming cells) from the bone marrow of a healthy, matching donor. It is generally considered the best treatment for SCID and is currently the only cure. Gene therapy for SCID is still being studied. Doctors may consider it for patients who cannot have a transplant. Children with SCID should avoid any live vaccines. While waiting for a transplant, staying away from sick contacts helps prevent infections. Any infection must be treated aggressively with strong medicine.
When to see a doctor
Get medical help right away if your child shows any sign of infection. Infections that are minor in most people can be life-threatening for a child with SCID. Call 911 if your baby has trouble breathing, blue or gray skin, a seizure, or is hard to wake. If a baby has repeated serious infections, chronic diarrhea, rashes, or poor growth, ask a doctor about immune system testing.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. Either kind of doctor can watch your child's growth and everyday health between specialist visits. They can also help you keep track of test results and care from the specialist team.
Common questions
Is ADA deficiency inherited?
Yes. It is inherited in an autosomal recessive pattern, so both copies of the ADA gene must be changed. Each parent carries one changed copy and usually has no signs.
Can ADA deficiency be cured?
A stem cell transplant from a matching donor is currently the only cure. Enzyme replacement therapy is a treatment, not a cure. Gene therapy is still being studied for SCID.
How is ADA deficiency found?
Newborn screening can find SCID early in most states. A low result leads to more blood tests. Doctors confirm with blood tests and genetic or biochemical tests, and they check how well the ADA enzyme works.
Does everyone with ADA deficiency get very sick?
No. About 80 percent have ADA-SCID and get sick in the first 6 months of life. About 15 to 20 percent have a milder form with later onset. Some people have partial ADA deficiency with no health problems.
Sources
- MedlinePlus Genetics - Adenosine deaminase deficiency
- National Organization for Rare Disorders (NORD) - Severe Combined Immunodeficiency
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
