Leukocyte adhesion deficiency type I (LAD-I) patients suffer from recurrent severe bacterial infections without pus formation. The molecular basis is deficiency of which protein?

• A Selectin ligand PSGL-1 on neutrophils
• B Myeloperoxidase in neutrophil azurophilic granules
• C NADPH oxidase gp91 subunit
• D CD18 (beta-2 integrin common chain), affecting LFA-1 and Mac-1 expression ✓

Explanation

LAD-I is caused by autosomal recessive mutations in ITGB2, encoding the CD18 (beta-2 integrin) subunit, which is required for surface expression of all beta-2 integrins (LFA-1, Mac-1, p150,95). Without functional beta-2 integrins, neutrophils cannot achieve firm adhesion to ICAM-1 on endothelium and fail to extravasate into tissues; hence infections proceed without pus. Peripheral blood neutrophilia develops as neutrophils remain in circulation. NADPH oxidase deficiency causes chronic granulomatous disease (CGD), not LAD.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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