A newborn is noted to have a persistent heart rate of 58 beats per minute with no relation to activity. ECG confirms complete atrioventricular block. The mother reports a self-limiting photosensitive facial rash two years ago and has anti-nuclear antibody positivity. Transplacental transfer of which maternal antibody is the most likely cause?
- A Anti-citrullinated protein IgG
- B Anti-Jo-1 IgG
- C Anti-Ro (SS-A) IgG ✓
- D Anti-mitochondrial IgG
Correct answer: C. Anti-Ro (SS-A) IgG
Explanation
Neonatal lupus results from passive transfer of maternal anti-Ro (SS-C), and less commonly anti-La (SS-B), IgG across the placenta. These antibodies bind antigens on the developing fetal cardiac conduction tissue, causing permanent fibrotic destruction of the AV node and congenital complete heart block, often detected between 16 and 24 weeks of gestation. Anti-Jo-1 marks antisynthetase myositis, and neither it nor the other listed antibodies cross-react with conduction tissue.
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.