A neonate has delayed separation of the umbilical cord beyond three weeks, followed by recurrent bacterial infections without pus formation. Neutrophil counts are high but neutrophils fail to adhere to endothelium or migrate to tissues. Which molecule is deficient?

• A Myeloperoxidase in neutrophil azurophilic granules
• B Selectin ligand sialyl-Lewis X on neutrophil surfaces
• C gp91phox subunit of the phagocyte NADPH oxidase
• D Beta-2 integrin CD18 subunit shared by LFA-1, Mac-1, and p150,95 ✓

Explanation

Leucocyte adhesion deficiency type 1 arises from mutations in ITGB2 encoding the CD18 beta chain common to the beta-2 integrins. Neutrophils cannot perform firm adhesion and transmigration, giving neutrophilia, absent pus, and delayed cord separation. Defective sialyl-Lewis X causes LAD type 2 with the same phenotype but also mental retardation and Bombay blood group. gp91phox and myeloperoxidase defects impair killing inside the phagosome, not adhesion or migration.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.