A newborn boy has delayed separation of the umbilical cord beyond 3 weeks. He later develops recurrent bacterial infections without pus formation, and peripheral blood shows striking neutrophilic leukocytosis during episodes despite absent neutrophils at infected tissues. Flow cytometry reveals absence of CD11/CD18 expression on leukocytes. The defective molecules belong to which family?

• A Beta-2 integrins mediating firm adhesion and transmigration ✓
• B Selectins mediating rolling along endothelium
• C Immunoglobulin superfamily adhesion molecules on endothelium
• D Chemokine receptors mediating directed migration

Explanation

Leukocyte adhesion deficiency type 1 arises from mutations in the ITGB2 gene encoding the CD18 beta chain shared by the beta-2 integrins (LFA-1, Mac-1, p150,95). Without these integrins, neutrophils roll normally but cannot adhere firmly to ICAM-1 or transmigrate into tissues, explaining absent pus, delayed cord separation, and paradoxical blood neutrophilia. Selectin defects underlie LAD type 2, a distinct entity with Bombay blood group phenotype.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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