A newborn has delayed separation of the umbilical cord beyond 3 weeks. By age 2 years he has recurrent bacterial infections without pus formation and persistent leukocytosis above 30,000/microliter. Flow cytometry shows absent expression of CD11a and CD11b on neutrophils. The deficient molecule family is:

• A Selectins on endothelial cells
• B Beta-2 integrins (CD18 heterodimers) ✓
• C NADPH oxidase subunits
• D Immunoglobulin Fc receptors

Explanation

Leukocyte adhesion deficiency type 1 arises from mutations in ITGB2 encoding CD18, the common beta chain of beta-2 integrins (LFA-1, Mac-1, p150,95). Neutrophils cannot adhere to endothelium or migrate to tissues, producing infections without pus, marked neutrophilia, and delayed umbilical stump separation. Selectin defects describe LAD type 2, and NADPH oxidase subunits define chronic granulomatous disease, in which pus and granulomas form normally.

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.