A 4-year-old boy suffers recurrent abscesses due to Serratia marcescens, Burkholderia cepacia, and Aspergillus, along with suppurative lymphadenitis. His neutrophils ingest organisms normally but fail to kill catalase-positive bacteria. Which test result confirms the suspected diagnosis?

• A Failure of neutrophil upregulation of CD11b after stimulation
• B Undetectable serum IgG with normal B cell numbers
• C Absent respiratory burst on the dihydrorhodamine oxidation assay ✓
• D Reduced platelet count with small platelet volume

Explanation

Chronic granulomatous disease results from defective NADPH oxidase components, most often the gp91phox encoded by CYBB. Neutrophils phagocytose normally but cannot generate the superoxide burst, so catalase-positive organisms that destroy endogenous peroxide survive. The dihydrorhodamine assay directly measures oxidative burst and is the confirmatory flow cytometric test. Low immunoglobulins and poor CD11b upregulation point to other immunodeficiencies.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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