A 2-year-old boy has recurrent abscesses due to Staphylococcus aureus, Serratia marcescens, and Aspergillus, along with suppurative lymphadenitis. Neutrophil count and chemotaxis are normal. The most likely underlying defect is:

• A Defective NADPH oxidase activity in phagocytes ✓
• B Failure of phagosomal alkalinization due to defective vacuolar ATPase
• C Absence of CD18 integrin subunit on neutrophils
• D Impaired fusion of lysosomes with phagosomes

Explanation

Chronic granulomatous disease results from mutations in components of the NADPH oxidase complex (gp91phox most commonly, X-linked), preventing the respiratory burst and generation of superoxide. Catalase-positive organisms survive intracellularly because they destroy host-derived hydrogen peroxide, while catalase-negative organisms are killed by their own peroxide. Absent CD18 defines leukocyte adhesion deficiency, and defective lysosomal fusion plus giant granules define Chediak-Higashi syndrome.

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.