A 45-year-old woman with primary Sjögren syndrome has a positive anti-Ro (SS-A) antibody. She becomes pregnant. Which fetal/neonatal complication is most directly attributable to transplacental passage of this antibody?
- A Congenital complete heart block due to antibody-mediated injury to the fetal cardiac conduction system ✓
- B Neonatal thrombocytopenia due to anti-platelet antibody cross-reactivity
- C Neonatal hemolytic anemia due to Ro antigen expression on red blood cells
- D Congenital hypothyroidism due to cross-reactivity with thyroid peroxidase
Explanation
Anti-Ro (SS-A) IgG antibodies cross the placenta and bind to Ro52/Ro60 antigens expressed on cardiac conduction cells of the fetal heart, triggering immune-mediated inflammation and fibrosis of the atrioventricular node, resulting in congenital complete heart block (third-degree AV block). This is the defining obstetric complication of maternal anti-Ro positivity (risk ~2% per pregnancy, higher if prior affected child) and may require pacemaker implantation. Neonatal lupus skin rash is another manifestation but is transient. Anti-platelet antibodies (anti-GPIIb-IIIa) cause neonatal thrombocytopenia in ITP.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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