A 4-year-old boy has recurrent infections with Staphylococcus aureus and Aspergillus. A nitroblue tetrazolium test is negative. The defect is in which enzyme?
- A Myeloperoxidase
- B NADPH oxidase ✓
- C Superoxide dismutase
- D Glucose-6-phosphate dehydrogenase
Correct answer: B. NADPH oxidase
Explanation
Chronic granulomatous disease is caused by a defect in NADPH oxidase, leading to absent respiratory burst and inability to kill catalase-positive organisms. The nitroblue tetrazolium test is negative because superoxide cannot be generated. Myeloperoxidase deficiency is usually mild; superoxide dismutase and G6PD defects do not cause this pattern.
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.