What are the congenital defects associated with Congenital Rubella Syndrome (CRS)?

Congenital Defects of Congenital Rubella Syndrome (CRS)

Congenital Rubella Syndrome causes a distinctive pattern of birth defects primarily affecting the auditory, ophthalmic, cardiac, and neurological systems, with up to 85% of fetuses infected during the first 8 weeks of gestation developing significant abnormalities. 1, 2

Major Organ Systems Affected

Auditory Defects

• Sensorineural hearing loss (most common manifestation) 1, 2
• Often permanent and may be detected months or years after birth

Ophthalmic Defects

• Cataracts (bilateral or unilateral) 1, 2, 3
• Microphthalmia (abnormally small eyes) 1, 3
• Glaucoma 1, 3
• Chorioretinitis 1, 2

Cardiac Defects

• Patent ductus arteriosus 1, 2, 4
• Peripheral pulmonary artery stenosis 1, 2, 4
• Atrial septal defects 1
• Ventricular septal defects 1
• Cardiomegaly 4

Neurological Defects

• Microcephaly 1, 2, 5
• Meningoencephalitis 1, 2
• Mental retardation/intellectual disability 1, 2, 3

Additional Manifestations

Growth Abnormalities

• Intrauterine growth retardation 1
• Postnatal growth retardation 1

Hematologic Abnormalities

• Thrombocytopenia 1, 2, 4
• Purpuric skin lesions 1, 2

Other Manifestations

• Hepatosplenomegaly 1, 2, 3
• Radiolucent bone defects 1, 2
• Pneumonitis 4

Risk Factors and Timing

• The risk of CRS is highest when maternal infection occurs during the first trimester:

  • 85% of infants develop defects when infection occurs in first 8 weeks 1
  • Risk decreases to approximately 52% when infection occurs between 9-12 weeks 1
  • Risk further decreases to 10-24% between weeks 13-16 2
  • Defects are rare after 20 weeks gestation 1, 2

• Even subclinical (inapparent) maternal rubella infection can cause congenital malformations 1

Long-Term Complications

• Late-onset manifestations may develop months or years after birth:
  • Diabetes mellitus 6, 7
  • Thyroid disease 6, 7
  • Growth hormone deficiency 6
  • Progressive panencephalitis 6
  • Late-onset glaucoma 3

Clinical Pearls

• Multi-organ involvement is typical (88% of cases) 3
• Mild CRS (e.g., slight cardiac involvement or hearing loss) may not be detected until months or years after birth 1
• Long-term follow-up is essential due to the potential for delayed manifestations 2, 3
• Cataracts and microphthalmia are significantly correlated with poor visual outcomes 3
• Glaucoma is significantly correlated with cataracts and microphthalmia 3

Prevention

• Vaccination is the most effective strategy to prevent CRS 1, 2
• Screening for rubella immunity should be performed in women of childbearing age 7
• Susceptible women should be vaccinated before pregnancy or in the immediate postpartum period 7

While new cases of CRS are rare in countries with established vaccination programs, the condition remains a concern due to imported cases from regions where rubella vaccination programs are not established 4.