A neonate born to a mother who had a low-grade febrile illness with rash in the first trimester is found to have bilateral cataracts, patent ductus arteriosus, and sensorineural deafness. Urine PCR confirms the suspected virus. Why does this virus cause such malformations while most other respiratory viruses do not?

• A It induces maternal IgG that cross-reacts with fetal neural tissue
• B It causes massive maternal viremia leading to placental infarction
• C It integrates into the fetal germline genome disrupting developmental genes
• D It crosses the placenta and inhibits mitotic division of actively dividing fetal cells during organogenesis ✓

Explanation

Congenital rubella syndrome follows maternal infection in the first trimester when organs are forming. The virus crosses the placenta, establishes persistent infection, and slows mitotic division of fetal cells, reducing cell number and producing the classic triad of cataract, cardiac defects (especially PDA and septal defects) and sensorineural deafness. Maternal antibodies cross-reactivity and germline integration have no basis; the teratogenesis depends directly on infection of dividing fetal tissue during organogenesis.

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.