Leukocyte adhesion deficiency (LAD) type I presents with recurrent bacterial infections, absent pus formation, and elevated blood neutrophil counts. The defective protein in LAD-I is:

• A Sialyl-Lewis X (selectin ligand) on neutrophils
• B CD18 (beta-2 integrin subunit) ✓
• C CXCR2 (IL-8 receptor)
• D NADPH oxidase complex (cytochrome b558)

Explanation

LAD-I is caused by deficiency of CD18, the common beta-2 integrin subunit shared by LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), and p150,95 (CD11c/CD18). Without these integrins, neutrophils cannot perform firm adhesion to ICAM-1 on endothelium and fail to transmigrate to sites of infection, resulting in neutrophilia in blood but absent tissue neutrophils and no pus. NADPH oxidase deficiency causes chronic granulomatous disease; defective selectin ligands cause LAD-II.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.