In chronic granulomatous disease (CGD), which enzyme defect causes recurrent catalase-positive bacterial and fungal infections?

• A Myeloperoxidase deficiency — impaired hypochlorous acid generation
• B Glucose-6-phosphate dehydrogenase deficiency — impaired HMP shunt in neutrophils
• C Chediak-Higashi syndrome — impaired phagolysosome fusion due to LYST gene mutation
• D NADPH oxidase deficiency — absent superoxide generation, impaired respiratory burst ✓

Explanation

CGD results from mutations in components of the NADPH oxidase complex (most commonly gp91phox, X-linked), abolishing superoxide production and the respiratory burst. Catalase-positive organisms (S. aureus, Aspergillus, Serratia) are particularly virulent in CGD because they destroy the small amounts of H2O2 they produce, denying neutrophils this killing mechanism. Myeloperoxidase deficiency impairs but does not abolish killing. Chediak-Higashi has partial albinism and giant granules due to LYST mutation.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.