T-B+ severe combined immunodeficiency due to IL-7Ralpha deficiency

T-B+ severe combined immunodeficiency due to IL-7Rα (interleukin-7 receptor alpha chain) deficiency is a rare, life-threatening primary immunodeficiency disorder caused by mutations in the IL7R gene located on chromosome 5p13. This condition is also known as IL-7Rα deficiency SCID or T-B+NK+ SCID due to IL-7Rα deficiency. It is characterized by a profound absence of T lymphocytes while B cells and natural killer (NK) cells are present in normal or near-normal numbers, though B cell function is impaired due to the lack of T cell help. The IL-7 receptor alpha chain plays a critical role in T cell development and thymic maturation, and its deficiency leads to a severe block in T lymphocyte differentiation. Affected infants typically present within the first months of life with recurrent, severe, and opportunistic infections including pneumonia, chronic diarrhea, oral candidiasis, and failure to thrive. Skin infections and sepsis are also common. Without treatment, the condition is fatal, usually within the first one to two years of life. The immune system is the primary body system affected, leaving patients vulnerable to bacterial, viral, fungal, and opportunistic pathogens. Live vaccines, such as BCG, can cause disseminated disease and must be avoided. The standard of care and most definitive treatment is hematopoietic stem cell transplantation (HSCT), which can reconstitute the T cell compartment and restore immune function, particularly when performed early in life before the onset of severe infections. Matched sibling donors provide the best outcomes, but haploidentical and unrelated donor transplants are also performed. Gene therapy approaches are under investigation. Newborn screening programs using the T-cell receptor excision circle (TREC) assay have improved early detection, enabling timely intervention and significantly better outcomes. Supportive care includes infection prophylaxis, immunoglobulin replacement therapy, and protective isolation.

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