A 3-year-old boy has recurrent Staphylococcus aureus abscesses, pneumonia with Serratia marcescens, and granulomatous colitis. Nitroblue tetrazolium test is negative. The defect in this patient's phagocytes is in which enzyme system?
- A Myeloperoxidase
- B NADPH oxidase ✓
- C Adenosine deaminase
- D Bruton tyrosine kinase
Correct answer: B. NADPH oxidase
Explanation
Chronic granulomatous disease results from NADPH oxidase deficiency, preventing respiratory burst and killing of catalase-positive organisms (S. aureus, Serratia, Burkholderia cepacia, Aspergillus). The NBT test measures superoxide production and is negative in CGD. Myeloperoxidase deficiency (A) is usually milder. Adenosine deaminase deficiency causes SCID. BTK deficiency causes XLA.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.