Question

Transplacental transfer of maternal anti-Ro (SS-A) and anti-La (SS-B) antibodies is most characteristically associated with which neonatal condition?

• A. Neonatal lupus erythematosus (with congenital complete heart block)
• B. Neonatal myasthenia gravis
• C. Haemolytic disease of the newborn
• D. Neonatal Graves’ (thyrotoxicosis)

Hint:

SS-A/SS-B antibodies crossing the placenta damage the fetal conduction system.

Answer 1

The Correct Option is A

Step 1: Identify the antibodies. Anti-Ro (SS-A) and anti-La (SS-B) are IgG autoantibodies found in mothers with SLE or Sjögren syndrome (sometimes asymptomatic). Being IgG, they cross the placenta.

Step 2: Link to the neonatal effect. These antibodies cause neonatal lupus erythematosus, whose hallmarks are an annular/photosensitive rash (transient, resolves as maternal antibody clears) and the serious, often permanent congenital complete heart block from immune-mediated damage to the developing AV node/conduction system. Cytopenias and hepatitis may also occur.

Step 3: Choose the answer. Anti-Ro/anti-La to neonatal lupus with congenital heart block.

Step 4: Why the others are wrong - neonatal myasthenia is from maternal anti-acetylcholine-receptor antibodies; haemolytic disease of the newborn is from anti-Rh(D)/blood group antibodies; neonatal Graves is from maternal TSH-receptor stimulating antibodies.

Key fact: Maternal anti-Ro/anti-La to neonatal lupus (rash + congenital complete heart block).