A 9-day-old neonate has persistent purulent omphalitis with delayed separation of the umbilical cord stump. Total leukocyte count is 42,000 per microliter with marked neutrophilia, yet the pus is scanty. Recurrent infections continue through infancy. Flow cytometry shows absence of CD18 expression on neutrophils. Defective adhesion of neutrophils in this child is due to loss of which molecules?

• A Selectins mediating rolling along endothelium
• B Complement receptors CR1 and CR3 mediating opsonized phagocytosis alone
• C Immunoglobulin superfamily adhesion molecules on endothelium
• D Beta-2 integrins LFA-1 and Mac-1 binding ICAM-1 ✓

Explanation

Leukocyte adhesion deficiency type 1 results from mutations in ITGB2 encoding the CD18 chain shared by the beta-2 integrins LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), and p150,95. Neutrophils cannot adhere firmly to endothelial ICAM-1 or migrate into tissues, producing delayed cord separation, profound neutrophilia, recurrent bacterial infections, and characteristically absent pus despite infection. Option A describes LAD type 2, caused by defective fucosylation of selectin ligands (sialyl-Lewis X), which also causes neutrophilia but spares CD18 expression.

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.