A neonate has delayed separation of the umbilical cord beyond 3 weeks, followed by recurrent infections with Staphylococcus aureus and enteric gram-negative bacilli. Abscesses contain surprisingly little pus. Peripheral blood shows neutrophilia. The underlying defect is:

• A Mutation of CYBB producing a nonfunctional phagocyte oxidase membrane component
• B Mutation of the gene encoding the beta-2 integrin subunit CD18, impairing leukocyte adhesion and extravasation ✓
• C Mutation of LYST causing defective fusion of lysosomal granules
• D Absence of myeloperoxidase from azurophilic granules

Explanation

Leukocyte adhesion deficiency type 1 arises from CD18 mutations abolishing the LFA-1, Mac-1, and p150,95 integrins. Neutrophils cannot adhere to endothelium or migrate into tissues, so infections lack pus, wounds heal poorly, and blood counts show persistent neutrophilia. CYBB mutation defines chronic granulomatous disease with granulomas rather than pus-free abscesses, and LYST mutation defines Chediak-Higashi with giant granules.

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.