Congenital Rubella Syndrome
A 3-week-old term infant whose unvaccinated mother had a febrile illness with a fine rash and painful joints at 9 weeks of gestation is referred because the red reflex is absent bilaterally. Birth weight was 2.1 kg. There is a continuous machinery murmur below the left clavicle, bounding pulses, hepatosplenomegaly, and blue-purple non-blanching papules. Auditory brainstem response testing fails bilaterally. What is the most likely causative infection?
- A.Rubella virusCorrect
- B.Cytomegalovirus
- C.Toxoplasma gondii
- D.Measles virus
Explanation
This is congenital rubella syndrome, whose classic triad is sensorineural deafness, cataracts and congenital heart disease, most typically patent ductus arteriosus or peripheral pulmonary artery stenosis. Cataracts obliterate the red reflex and produce leukocoria, which explains the white pupillary reflex; the continuous machinery murmur with bounding pulses is a patent ductus arteriosus; and failed auditory brainstem responses reflect sensorineural hearing loss, the single most common defect. The blue-purple non-blanching papules represent the blueberry muffin rash of dermal extramedullary haematopoiesis. Rubella is teratogenic when acquired in the first trimester, with the highest risk before 11 weeks of gestation, matching the maternal rash and arthralgia at 9 weeks. Cytomegalovirus is the commonest congenital infection overall and also causes a blueberry muffin rash, hearing loss and hepatosplenomegaly, but its signature findings are periventricular intracranial calcifications, microcephaly and chorioretinitis rather than cataracts and patent ductus arteriosus. Congenital toxoplasmosis causes the triad of hydrocephalus, diffuse intracranial calcifications and chorioretinitis, again without cataracts or a machinery murmur. Measles is not teratogenic in this pattern, causing fetal loss and prematurity instead. Leukocoria always requires urgent ophthalmological referral because retinoblastoma, cataract and Coats disease are other important causes.
Why each option
- A.
- Correct. Cataract with leukocoria, patent ductus arteriosus and sensorineural deafness after first-trimester maternal rash is congenital rubella syndrome.
- B.
- Congenital cytomegalovirus causes periventricular calcifications, microcephaly, chorioretinitis and hearing loss, but not cataracts with patent ductus arteriosus.
- C.
- Congenital toxoplasmosis causes hydrocephalus, diffuse intracranial calcifications and chorioretinitis rather than cataract and structural heart disease.
- D.
- Measles in pregnancy causes fetal loss and preterm birth but does not produce this constellation of congenital defects.
Reference: AAP Red Book, 2024, Rubella; Nelson Textbook of Pediatrics, 22nd ed., 2024
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