A young male patient has recurrent abscesses due to Staphylococcus aureus, Burkholderia cepacia, Serratia marcescens, and Aspergillus, along with granulomatous lymphadenitis. Dihydrorhodamine flow cytometry shows absent fluorescence burst from stimulated neutrophils. The fundamental cellular defect is failure of:

• A Phagolysosome acidification due to defective proton pump assembly
• B Fusion of lysosomes with phagosomes secondary to abnormal microtubule transport
• C Assembly of the phagocyte NADPH oxidase complex generating superoxide ✓
• D Opsonization because of inability to synthesize C3 convertase

Explanation

Chronic granulomatous disease results from mutations affecting any component of the phagocyte NADPH oxidase system, most commonly gp91phox encoded on the X chromosome. Without superoxide generation, the oxidative burst fails and catalase-positive organisms that neutralize endogenous hydrogen peroxide survive inside phagocytes, driving persistent cell-mediated recruitment and granuloma formation. Option B describes Chediak-Higashi syndrome, which shows giant granules rather than an absent respiratory burst.

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.