Congenital rubella syndrome pathophysiology

The pathogenesis of congenital rubella syndrome is multifactorial. However, pregnant women who are not vaccinated against rubella are at high risk of contracting the infection. If they get infected during pregnancy, the virus can infect the placenta and spread to the fetus, leading to disruption of the normal process of organogenesis. The degree of severity of malformations depends on the gestational age of the onset of infection. The highest risk of fetal anomalies or poor pregnancy outcomes such as spontaneous abortion and stillbirth is highest if a woman becomes infected prior to conception or in the in the first 8-10 weeks of gestation.^{[1][2][3][4][5]}

The pathogenesis of congenital rubella syndrome (CRS) is believed to be multifactorial. In an attempt to explain the pathogenesis, the following must be noted:^{[1][2][3][4][5]}

• Pregnant women who are not vaccinated against rubella virus are at risk of contracting the infection. It must be noted however, that not every pregnant woman’s infection results in vertical transmission to her fetus. In addition, not every fetus infected with rubella virus has fetal abnormalities or CRS.
• The typical clinical course of CRS usually begins with a pregnant woman being exposed to the virus via the respiratory route. The virus then infects the placenta and spreads to the fetus. This results in systemic inflammation in the fetus and multiple fetal anomalies, due to disruption of organogenesis.
• Infected cells of the placenta enter the fetal circulation and spread to to various organs, such as the heart, brain, eyes and ears, resulting in thrombosis or ischemic lesions in these organs.
• In rubella-infected human fetal cells, interferons and cytokines are up-regulated. Hence, the immune system is thought to play a role in disrupting the normal differentiation of cells and result in the various congenital defects observed in congenital rubella syndrome.
• The timing of the maternal infection has important implications on the fetus. If the woman is infected just before conception or during the first 8-10 weeks of gestation, severe fetal anomalies are most likely to occur, including stillbirth. However, beyond 16 weeks of gestation, rarely any fetal defects are associated with maternal rubella infection.

• Noninflammatory necrosis is observed in the epithelium of the chorion, as well as in the endothelial cells.^[3]
• Cell mitosis is inhibited as a result of inhibition of actin assembly.^[3]