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Blood and immune system diseases

Severe combined immunodeficiency (SCID)

A group of inborn diseases in which the immune system hardly works at all. Severe and frequent infections occur in infancy.

Not part of the panel of Türkiye's National Newborn Screening Programme (heel-prick test). Source

Prepare an emergency card

This page is translated from the Turkish original.

This disease is followed through the “Blood and immune system diseases” group.

Understanding the disease

This section has not yet been reviewed by a physician. It summarises patient information from sources such as MedlinePlus, Orphanet and the NHS in plain language. The disease can differ from person to person; talk to your doctor about diagnosis and treatment.

What happens in this disease?

Lymphocytes are white blood cells that protect the body from germs. In SCID, these cells, especially T cells, cannot develop or do not work. The immune system cannot fight off bacteria, viruses and fungi. The disease is caused by a change in one of more than 20 genes. The most common type is X-linked SCID.

Which symptoms can occur?

In the first months, babies are protected by antibodies passed on from the mother. Symptoms usually begin between 3 and 6 months.

  • Frequent and severe infections, for example pneumonia
  • Infections that do not respond well to treatment
  • Thrush in the mouth, meaning a fungal infection
  • Long-lasting diarrhea
  • Poor weight gain and slow growth
  • Skin rash

How is it diagnosed?

In some countries, it is detected shortly after birth through newborn screening. This test measures a trace of T cell production in blood from the heel. If the result is low, a blood count and lymphocyte tests are done. A genetic test determines the type of the disease.

Treatment and care

The most effective treatment and the only lasting solution is a stem cell (bone marrow) transplant. The transplant is preferably done in the first months of life. Until the transplant, the baby is protected from infections and live vaccines are not given. For the type caused by ADA deficiency, enzyme treatment may be used. For this type, there is also a gene therapy approved in Europe. Gene therapy for the other types is being researched. The doctor who follows the disease decides which treatment is suitable.

For the family: inheritance and genetic counselling

Most types are passed on through recessive inheritance. For a couple who are both carriers, the chance of having an affected child is 1 in 4 in each pregnancy. Recessive diseases may be more common in marriages between relatives. It has been reported to be more common in families of Turkish origin. The X-linked type, on the other hand, mostly affects boys. A mother who is a carrier has a 1 in 4 chance of having an affected boy in each pregnancy. Genetic counselling guides future pregnancies.

Source: NORD: Severe Combined Immunodeficiency · MedlinePlus Genetics: X-linked severe combined immunodeficiency · MedlinePlus Genetics: Adenosine deaminase deficiency · EMA: Strimvelis (ADA-SCID gen tedavisi) EPAR

Key facts

When does it usually start?
Infancy, Newborn period

These facts are taken from Orphanet and MedlinePlus records (last checked: October 7, 2026). Frequency values are approximate ranges.

You are not alone: patient associations in Türkiye

Non-profit patient and family organizations in Türkiye working on this disease or disease group. Links are for information; Doktorclub is not affiliated with these organizations and does not endorse them.

We could not find a patient association specific to this disease.

For all rare diseases: Nadir Hastalıklar Federasyonu

Support and help

Doktorclub does not diagnose, recommend treatments or refer you to hospitals or doctors. These pages are meant to help you talk with your doctor.

News about SCID

Clinical trials (ClinicalTrials.gov)

A clinical trial is a regulated study that tests whether a new treatment is safe and whether it works, in patients who volunteer. Most trials look for a certain age, genetic change and health condition. Taking part is voluntary.

This list is not a treatment recommendation. Treatments tested in phase 1–3 trials are investigational (experimental): their efficacy and safety have not yet been proven and they are not approved treatments. Taking part depends on each trial’s criteria and a physician’s assessment; the first step is to talk to the doctor who manages your care.

Questions you can ask your doctor

  • Could this trial be suitable for us?
  • If we take part, how would current treatment and check-ups be affected?
  • Where does the trial take place, and how are travel and accommodation handled?
  • What happens if we want to leave the trial?

ClinicalTrials.gov lists 13 active interventional studies for this disease. 4 are recruiting now; none has a site in Türkiye. Last checked: October 7, 2026.

Selected records (studies with a site in Türkiye first):

See all studies on ClinicalTrials.gov · Joining clinical trials

Blood and immune system diseases: other news

Medical codes (for talking with your doctor and finding sources)

These codes identify the disease in international classifications and databases. They can help when you talk with your doctor or look for reliable sources.

Orphanet code: ORPHA:183660 · ICD-11 4A01.10

Codes checked against WHO ICD-11 and Orphanet on October 7, 2026.

This page provides general information and does not replace diagnosis or treatment. Talk to your doctor about symptoms, diagnosis and treatment.

The information on these pages is for general information only and does not replace medical advice. Talk to your doctor about diagnosis and treatment decisions. In an emergency in Türkiye, call 112.

Every update is based on an open source and labeled with its level of evidence. No advertising and no drug brand names. Our scientific principles

This page was translated from Turkish by the Doktorclub editorial team.