A newborn develops profound bradycardia requiring pacing for complete atrioventricular block. The mother has a history of Sjogren syndrome and is positive for anti-Ro antibodies. What is the underlying mechanism of this cardiac lesion?

• A Autosomal recessive mutation in the SCN5A gene
• B Transplacental transfer of maternal anti-Ro/SSA antibodies binding fetal cardiac conduction tissue ✓
• C Maternal lithium therapy causing fetal atrioventricular node toxicity
• D Fetal myocarditis due to coxsackievirus B infection

Explanation

Neonatal lupus occurs when maternal anti-Ro/SSA and anti-La/SSB antibodies cross the placenta and bind apoptotic fetal cardiocytes, triggering inflammation and fibrosis of the atrioventricular node, resulting in irreversible congenital complete heart block often needing pacemaker implantation. The mother may have SLE or Sjogren syndrome yet be asymptomatic. SCN5B mutations cause familial conduction disease, and lithium causes Ebstein anomaly rather than heart block.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.