A 6-year-old child has recurrent severe bacterial infections and has been hospitalised with Staphylococcus aureus lymphadenitis. Nitroblue tetrazolium (NBT) test is negative (no colour change). The diagnosis is:

• A Chronic granulomatous disease (CGD) ✓
• B Chediak-Higashi syndrome
• C Myeloperoxidase deficiency
• D Leukocyte adhesion deficiency (LAD)

Explanation

Chronic granulomatous disease results from defects in NADPH oxidase (most commonly X-linked gp91phox/CYBB subunit), abolishing the respiratory burst and superoxide generation. The NBT test (now largely replaced by flow cytometric DHR test) measures oxidative burst: normal neutrophils reduce yellow NBT dye to blue-purple formazan; CGD neutrophils produce no superoxide and cannot reduce NBT (negative result). CGD patients suffer recurrent catalase-positive bacterial and fungal infections (S. aureus, Aspergillus, Nocardia). Chediak-Higashi shows giant lysosomal granules and partial albinism. Myeloperoxidase deficiency impairs halide-mediated killing but NBT is still positive. LAD lacks CD18 integrins causing failure of neutrophil adhesion.

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

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Written and medically reviewed by the StethoPrep medical team.