A newborn develops complete heart block requiring pacing. The mother has a history of arthralgia and photosensitive rash. Which maternal autoantibody is most likely responsible?

• A Anti-dsDNA
• B Anti-U1 RNP
• C Anti-Smith
• D Anti-Ro (SSA) ✓

Explanation

Transplacental passage of IgG anti-Ro (and anti-La) antibodies causes neonatal lupus, and the cardiac manifestation is congenital complete heart block due to fibrosis of the fetal conduction system. Anti-dsDNA and anti-Smith define maternal SLE activity but do not cross-react with fetal cardiac tissue, so they do not cause heart block. Anti-La may coexist but anti-Ro is the strongest single marker.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.