Home/Rare Diseases/Severe Combined Immunodeficiency
Blood & Immune

Severe Combined Immunodeficiency

Affects approximately
1 in 50,000 to 100,000 births

Also known as: SCID, bubble boy disease

Severe Combined Immunodeficiency

About Severe Combined Immunodeficiency

Severe combined immunodeficiency (SCID) represents a group of rare genetic disorders affecting development and function of T lymphocytes and B lymphocytes, essential for adaptive immune responses. Multiple genetic causes exist, including IL2RG (X-linked SCID), ADA deficiency, RAG1/RAG2 deficiencies, and others. Without functional T and B cells, infants are profoundly immunocompromised and susceptible to overwhelming infections from bacteria, viruses, fungi, and parasites. Infants typically present within the first weeks to months of life with severe infections including opportunistic infections like Pneumocystis pneumonia and candidiasis. Without intervention, death typically occurs by age 1 year from uncontrolled infection. Historically, treatment was hematopoietic stem cell transplantation (bone marrow transplant), which could restore immune function in surviving patients. Gene therapy approaches using autologous hematopoietic stem cell modification are emerging and show promise for restoring immune function in many SCID forms.

Common Symptoms

  • Recurrent, severe infections (bacterial, viral, fungal, parasitic)
  • Severe diarrhea and malabsorption
  • Failure to thrive
  • Delayed growth and development
  • Recurrent infections unresponsive to antibiotics
  • Opportunistic infections including Pneumocystis pneumonia and candidiasis

Who It Affects

Symptoms typically emerge in the first weeks to months of life. Multiple genetic forms with autosomal recessive or X-linked inheritance. Affects males and females (X-linked form) or both equally (autosomal forms).

Getting Involved in Clinical Trials

Gene therapy for several forms of SCID (including ADA-SCID and IL2RG-SCID) has demonstrated success in clinical trials, with treated patients achieving immune reconstitution. Early diagnosis through newborn screening (now available in many states) allows early intervention. The Jeffrey Modell Foundation and patient organizations provide information on SCID and clinical trials. If SCID is diagnosed, discuss with your immunologist about treatment options including gene therapy versus hematopoietic stem cell transplantation. Genetic counseling is essential for affected families. Isolation and infection prevention are critical until immune reconstitution is achieved through treatment.

Trusted Sources

Active Clinical Trials for Severe Combined Immunodeficiency

Finding trials for Severe Combined Immunodeficiency...

Related Blood & Immune Conditions

Blood & Immune

Sickle Cell Disease

Sickle cell disease is an inherited blood disorder where hemoglobin polymerizes under low oxygen, causing red blood cell...

Blood & Immune

Thalassemia

Thalassemia is an inherited blood disorder where reduced or absent production of one type of hemoglobin chain causes sev...

Blood & Immune

Mastocytosis

Mastocytosis is a rare hematological disorder characterized by clonal expansion of mast cells in bone marrow, organs, an...