A newborn boy has delayed separation of the umbilical cord beyond 3 weeks. He later develops recurrent infections with Staphylococcus aureus and enteric gram-negative bacteria characterized by absence of pus despite marked tissue necrosis. Neutrophil counts are persistently above 25,000/microliter. The most likely molecular defect is:

• A Mutation of the STAT3 gene impairing Th17 differentiation
• B Mutation of the NADPH oxidase complex gp91phox subunit
• C Deficiency of myeloperoxidase in azurophilic granules
• D Mutation of the beta-2 integrin subunit CD18 ✓

Explanation

Leukocyte adhesion deficiency type 1 arises from CD18 mutations, abolishing the beta-2 integrins LFA-1, Mac-1, and p150,95. Neutrophils cannot adhere to endothelium or migrate into tissues, so infections lack pus, wound healing fails, the umbilical stump separates late, and blood neutrophil counts are high because cells cannot leave the circulation. gp91phox defects define chronic granulomatous disease, which produces granulomas rather than pusless necrosis.

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.