Question

A 6-month-old infant presents with frequent infections and failure to thrive. Tests show adenosine deaminase (ADA) deficiency. Which immunodeficiency disorder is most likely responsible?

• A. Severe Combined Immunodeficiency (SCID)
• B. Hypogammaglobulinemia
• C. DiGeorge syndrome
• D. Wiskott-Aldrich syndrome

Hint:

ADA deficiency in an infant with recurrent infections = SCID.

Answer 1

The Correct Option is A

Concept: Adenosine deaminase deficiency causes accumulation of toxic purine metabolites, leading to lymphocyte dysfunction. It is a classic cause of severe combined immunodeficiency.

Step 1: Identify clinical features.
Frequent infections and failure to thrive in infancy suggest a severe immunodeficiency.

Step 2: Use enzyme clue.
ADA deficiency is strongly associated with: \[ \text{Severe Combined Immunodeficiency} \]

Step 3: Understand immune defect.
SCID affects both T-cell and B-cell immune function, leading to severe recurrent infections. Therefore, the correct answer is Severe Combined Immunodeficiency (SCID).