A neonate born to a mother with systemic lupus erythematosus presents at 3 weeks with complete heart block (ventricular rate 45/min) on ECG. The baby appears comfortable. Which maternal antibody is responsible and what is the mechanism?
- A Anti-Ro/SSA antibodies cross the placenta and cause inflammation and fibrosis of the atrioventricular conduction system ✓
- B Anti-dsDNA antibodies cross the placenta and bind to cardiac myocytes, causing apoptosis
- C Anti-phospholipid antibodies cause thrombosis of the AV node vasculature
- D Anti-histone antibodies bind to His bundle proteins, causing conduction block
Correct answer: A. Anti-Ro/SSA antibodies cross the placenta and cause inflammation and fibrosis of the atrioventricular conduction system
Explanation
Neonatal lupus heart block is caused by transplacental passage of maternal anti-Ro/SSA (and anti-La/SSB) antibodies. These antibodies bind to Ro antigens on foetal cardiac conduction tissue, triggering complement-mediated inflammation and subsequent fibrosis of the AV node, causing permanent complete heart block. Anti-dsDNA, anti-phospholipid, and anti-histone antibodies are not responsible for this specific complication.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.