A newborn boy's umbilical cord stump has not separated by 6 weeks. He subsequently develops recurrent bacterial infections with striking neutrophilia (30,000 per microliter) yet almost no pus at infected sites. Flow cytometry of neutrophils would most likely demonstrate absence of:
- A CD62L (L-selectin) on the neutrophil surface
- B CD18, the beta-2 integrin chain shared by CD11a, CD11b, and CD11c ✓
- C Sialyl-Lewis X modified PSGL-1 ligand
- D CD64 (FcgammaRI) expression
Correct answer: B. CD18, the beta-2 integrin chain shared by CD11a, CD11b, and CD11c
Explanation
Leukocyte adhesion deficiency type 1 is caused by mutations in ITGB2 encoding CD18, the common beta chain of the beta-2 integrins (LFA-1, Mac-1, p150,95). Without these integrins neutrophils adhere poorly to endothelium and migrate into tissues, giving delayed cord separation, recurrent infection, absent pus, and persistent neutrophilia in blood. CD62L or sialyl-Lewis X defects correspond to leukocyte adhesion deficiency type 2, which presents with Bombay blood group and facial dysmorphism rather than delayed cord loss.
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.