A 5-year-old boy has recurrent abscesses due to Staphylococcus aureus, Burkholderia cepacia, and Aspergillus, along with suppurative lymphadenitis. His grandmother had a similar childhood history. The most appropriate screening test and its expected result are:

• A Nitroblue tetrazolium dye reduction test showing failure of granulocytes to reduce the dye ✓
• B Serum IgE level showing values below 50 IU/mL
• C Flow cytometry for CD18 showing absent expression on granulocytes
• D Dihydrorhodamine assay showing exaggerated oxidative burst

Explanation

Chronic granulomatous disease, usually X-linked via CYBB encoding gp91phox, cripples the phagocyte NADPH oxidase, so the respiratory burst cannot generate superoxide. Catalase-positive organisms survive inside phagocytes because they destroy endogenous hydrogen peroxide. Both the nitroblue tetrazolium slide test and dihydrotetrazolium-based flow assays show absent or severely reduced dye reduction; an exaggerated burst is impossible. Low IgE points toward hyper-IgE syndrome, and absent CD18 defines leukocyte adhesion deficiency.

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.