Deficiency of which complement component produces the most severe recurrent Neisseria infections due to inability to form the membrane attack complex?
- A C5b deficiency or C6/C7/C8/C9 (terminal complement component deficiency) ✓
- B C3 deficiency
- C Factor I deficiency (complement regulatory)
- D C1q deficiency
Explanation
Deficiencies of terminal complement components — C5b and especially C6, C7, C8, and C9 (the proteins that form the membrane attack complex, MAC/C5b-9) — result in inability to lyse encapsulated gram-negative bacteria. Neisseria meningitidis and Neisseria gonorrhoeae are exquisitely sensitive to MAC-mediated killing; patients with terminal complement deficiencies suffer recurrent and severe Neisseria bacteremia/meningitis. C3 deficiency causes severe pyogenic infections and opsonization defects. Factor I deficiency causes uncontrolled C3 consumption. C1q deficiency leads to susceptibility to pyogenic infections and SLE-like disease via impaired apoptotic body clearance.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.