A child has recurrent bacterial infections, absent pus, and marked neutrophilia, but CD18 expression on lymphocytes is normal. Neutrophils fail to roll on activated endothelium in flow-chamber assays. What is the underlying defect?

• A Mutation of ITGB2 preventing beta-2 integrin surface expression
• B Loss of gp91phox subunit of NADPH oxidase
• C Deficiency of the common gamma chain of Fc receptors
• D Defective fucosylation of sialyl-Lewis X, the selectin ligand ✓

Explanation

LAD type II results from defective GDP-fucose transport or fucosyltransferase activity, so leukocytes cannot synthesize sialyl-Lewis X, the ligand for E-selectin and P-selectin. Rolling fails, neutrophils never reach tissue, and patients also have Bombay blood group phenotype and short stature. Normal CD18 excludes LAD-I, and gp91phox loss defines chronic granulomatous disease, where adhesion and pus formation are intact.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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