A newborn boy has delayed separation of the umbilical cord beyond three weeks, followed by recurrent bacterial infections without pus formation. Total leukocyte count is markedly elevated and flow cytometry shows absence of beta-2 integrins (CD11/CD18) on neutrophils. The fundamental cellular defect is impaired:

• A Oxidative burst following NADPH oxidase assembly
• B Phagosome-lysosome fusion
• C Firm adhesion of neutrophils to endothelium via ICAM-1 binding ✓
• D Rolling of neutrophils along endothelium via selectins

Explanation

Leukocyte adhesion deficiency type 1 results from CD18 (beta-2 integrin chain) deficiency, preventing CD11/CD18 heterodimers from binding ICAM-1 on activated endothelium. Neutrophils roll normally via selectins but cannot adhere firmly or transmigrate, producing pusless infections, delayed cord separation, and striking neutrophilia. NADPH oxidase failure defines chronic granulomatous disease, phagolysosomal fusion failure defines Chediak-Higashi, and selectin defects cause LAD type 2.

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.