Overview
T-B+ severe combined immunodeficiency due to gamma chain deficiency, also known as X-linked severe combined immunodeficiency (X-SCID) or SCID-X1, is the most common form of severe combined immunodeficiency. It is caused by mutations in the IL2RG gene, which encodes the common gamma chain (γc), a shared subunit of the receptors for several interleukins (IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21). Because these cytokine signaling pathways are critical for the development and function of the immune system, affected individuals have profoundly impaired immunity characterized by the absence or very low numbers of T cells and natural killer (NK) cells, while B cells are present but functionally deficient (T-B+NK- SCID). Infants with this condition typically present within the first few months of life with recurrent, severe, and often life-threatening infections, including pneumonia, chronic diarrhea, oral thrush (candidiasis), and skin infections. Failure to thrive is common. Without treatment, affected infants are highly susceptible to opportunistic infections caused by bacteria, viruses, fungi, and protozoa, and the condition is usually fatal within the first one to two years of life. Live vaccines, such as BCG and rotavirus, can cause disseminated disease and must be avoided. The standard of care and most effective treatment is hematopoietic stem cell transplantation (HSCT), which can be curative, particularly when performed early in life and ideally from an HLA-matched donor. Newborn screening programs using the T-cell receptor excision circle (TREC) assay have significantly improved early detection and outcomes. Gene therapy has emerged as a promising alternative, especially for patients lacking a suitable donor, and clinical trials have demonstrated long-term immune reconstitution. Enzyme replacement therapy is not applicable to this form of SCID. Supportive care includes infection prophylaxis, immunoglobulin replacement therapy, and protective isolation until definitive treatment is achieved.
Also known as:
Clinical phenotype terms— hover any for plain English:
X-linked recessive
Carried on the X chromosome; typically affects males more than females
Infantile
Begins in infancy, roughly 1 month to 2 years old
FDA & Trial Timeline
9 eventsShenzhen Geno-Immune Medical Institute — PHASE1, PHASE2
Shenzhen Geno-Immune Medical Institute — NA
St. Jude Children's Research Hospital — PHASE1, PHASE2
Leiden University Medical Center — NA
University of California, San Francisco — PHASE1, PHASE2
David Williams — PHASE1
Fondazione Telethon
National Heart, Lung, and Blood Institute (NHLBI)
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for T-B+ severe combined immunodeficiency due to gamma chain deficiency.
4 clinical trialsare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Rare Disease Specialist
Rare Disease Specialist
Rare Disease Specialist
Treatment Centers
8 centersCincinnati Children's Hospital Medical Center
📍 Cincinnati, Ohio
Boston Childrens Hospital
📍 Boston, Massachusetts
Stanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
Travel Grants
No travel grants are currently matched to T-B+ severe combined immunodeficiency due to gamma chain deficiency.
Community
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Start the conversation →Latest news about T-B+ severe combined immunodeficiency due to gamma chain deficiency
Disease timeline:
New recruiting trial: Autologous Gene Therapy for Artemis-Deficient SCID
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Genetic Basis of Immunodeficiency
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: SCID-X1 Gene Therapy Via Intravenous Lentiviral (Ivlv-X1) Injection
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Targeting Real World Usage In Stroke Treatment
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Study of Populations at Risk of Developing Chronic Hepatitis Linked to Chronic Enteric Virus Infection in Patients With Primary Immunodeficiency and Secondary Humoral Deficiency
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: The Experience of Screening for SCID
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Phase I/II Clinical Trial Stem Cell Gene Therapy in RAG1-Deficient SCID
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Gene Therapy for ADA-SCID Using an Improved Lentiviral Vector (Ivlv-ADA)
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New recruiting trial: Gene Therapy for Adenosine Deaminase Severe Combined Immune Deficiency Using Peripheral Blood and EFS ADA Vector
A new clinical trial is recruiting patients for T-B+ severe combined immunodeficiency due to gamma chain deficiency
New trial: Phase I/II Trial of Lentiviral Gene Transfer for SCID-X1 With Low Dose Targeted Busulfan Conditionin
Phase PHASE1 trial recruiting. autologous CD34+ cell transduced with G2SCID vector
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Common questions about T-B+ severe combined immunodeficiency due to gamma chain deficiency
What is T-B+ severe combined immunodeficiency due to gamma chain deficiency?
T-B+ severe combined immunodeficiency due to gamma chain deficiency, also known as X-linked severe combined immunodeficiency (X-SCID) or SCID-X1, is the most common form of severe combined immunodeficiency. It is caused by mutations in the IL2RG gene, which encodes the common gamma chain (γc), a shared subunit of the receptors for several interleukins (IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21). Because these cytokine signaling pathways are critical for the development and function of the immune system, affected individuals have profoundly impaired immunity characterized by the absence or very
How is T-B+ severe combined immunodeficiency due to gamma chain deficiency inherited?
T-B+ severe combined immunodeficiency due to gamma chain deficiency follows a x-linked recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does T-B+ severe combined immunodeficiency due to gamma chain deficiency typically begin?
Typical onset of T-B+ severe combined immunodeficiency due to gamma chain deficiency is infantile. Age of onset can vary across affected individuals.
Are there clinical trials for T-B+ severe combined immunodeficiency due to gamma chain deficiency?
Yes — 4 recruiting clinical trials are currently listed for T-B+ severe combined immunodeficiency due to gamma chain deficiency on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat T-B+ severe combined immunodeficiency due to gamma chain deficiency?
5 specialists and care centers treating T-B+ severe combined immunodeficiency due to gamma chain deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.