Patients born with an adenosine deaminase deficiency would likely suffer from

• A. Acquired immunodeficiency syndrome (AIDS)
• B. DiGeorge syndrome
• C. Severe combined immunodeficiency
• D. Wiskott-Aldrich syndrome

Answer: (C)

Adenosine deaminase deficiency causes a toxic buildup of deoxyadenosine and dATP inside lymphocytes, which disrupts their development and function. This toxicity particularly cripples both T cells and B cells, leading to a failure of cellular and humoral immunity. The result is severe combined immunodeficiency, a condition where the immune system is profoundly deficient on multiple fronts, making infants extremely susceptible to life‑threatening infections.

AIDS arises from an acquired HIV infection, not a genetic enzyme deficiency, so it is not the inherited immunodeficiency described here. DiGeorge syndrome involves thymic absence or hypoplasia, mainly a T‑cell defect due to a developmental abnormality, not a broad failure of both T and B cells from a metabolic block. Wiskott‑Aldrich syndrome is X‑linked and involves thrombocytopenia and eczema with immunodeficiency, but its cause is a cytoskeletal signaling defect, not ADA deficiency.