A patient with chronic granulomatous disease (CGD) suffers recurrent infections with catalase-positive organisms (S. aureus, Aspergillus). The molecular defect involves:

• A Absence of myeloperoxidase in primary granules of neutrophils
• B Lack of CD18 (beta-2 integrin) causing LAD syndrome
• C Deficiency of NADPH oxidase (gp91phox or p47phox) preventing respiratory burst ✓
• D Absent G-actin polymerization preventing neutrophil chemotaxis

Explanation

Chronic granulomatous disease results from mutations in NADPH oxidase components (most commonly X-linked gp91phox/CYBB; autosomal p47phox, p67phox). NADPH oxidase generates superoxide radicals during the oxidative burst, essential for killing catalase-positive organisms. Catalase-positive bacteria can neutralize their own H2O2, leaving neutrophils with no reactive oxygen species to kill them. MPO deficiency causes mild immunodeficiency with intact H2O2. LAD is CD18 deficiency.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.