CONGENITAL RUBELLA SYNDROME

 CONGENITAL RUBELLA SYNDROME 

Source:kanski

Rubella virus - Togavirus family (RNA virus.) 

Transmission 

• Congenital rubella results from the transplacental transmission of virus to the foetus from an infected mother. 
• Maternal Rubella infection acquired during first trimester of pregnancy (second or third month).
• Usually occurs in the first trimester of pregnancy. 
• That may lead to serious chronic fetal infection and malformations. 
• Risk to the foetus is related to the stage of gestation at the time of maternal infection. 
• 50% cases- first 8 weeks ; 33%-9-12 weeks ; 10% - 13-24 weeks 
• Virus spreads through blood stream to various tissues including placenta. 

Note: Congenital rubella can be prevented by vaccination of the mother. Since the rubella vaccine is toxic to the foetus, it must therefore, be administered atleast 3 months before the pregnancy. 

 Rubella syndrome 

Congenital rubella cataract may occur alone or as part of the classic rubella syndrome which consists of: 

1. Ocular defects

• Congenital cataract
• Salt & pepper chorioretinopathy 
• Microphthalmos 
• Cloudy cornea
• Poorly dilating pupil 

2. Ear defects 

• Deafness due to destruction of organ of Corti 

3. Heart defects 

• Patent ductus arteriosus 
• Pulmonary stenosis 
• Ventricular septal defect 

Systemic features: 

1. Intrauterine growth retardation
2. Congenital heart disease eg. ASD,VSD,PDA
3. Deafness
4. Microcephaly & mental retardation 

Ocular features: 

1. Congenital nuclear cataract or total cataract 
2. Glaucoma 
3. Clouding of cornea 
4. Anterior uveitis-iris atrophy 
5. Chorioretinitis 
6. Microophthalmos 
7. Keratitis  
8. Extreme refractive error 

 Microophthalmos  

• Occurs in 10% cases. 
• Due to growth retardation effect of virus on developing tissues. 

Rubella Cataract 

• Occurs in 15% cases.
• may be unilateral or bilateral
• although lens opacity usually present at birth, cataract may develop several weeks/months later.
• After 6 weeks of gestation, virus is incapable of crossing lens capsule, so lens is immune.
• Rubella cataract typically, the child is born with ‘pearly white’ nuclear cataract.
• It is progressive type of cataract. 
• Lens matter may remain soft or even liquify (Congenital Morgagnian Cataract).
• The opacity involves nucleus with dense pearly appearance Or it involves most of the lens with diffuse opacity. 
• The virus persists within lens for upto 3 years after birth. Therefore removal of such a cataract is usually followed by a severe inflammatory reaction (uveitis or even endophthalmitis). So adequate precaution taken during cataract extraction & avoid exposure to cortical nucleus. 

Glaucoma  

• Occurs in 10% cases. 
• 2 types  - Congenital    - Acquired 
• Occurs due to angle dysyeresis  (or)  secondary to iridocyclitis. 

Iris hypoplasia 

• Seen if infection is present in early pregnancy 

Chronic iridocyclitis 

• with iris & ciliary body pigment epithelium necrosis. 

Corneal clouding 

• Secondary to endothelitis & uncontrolled IOP. 

Pendular Nystagmus: 

• latent, fine or jerky 

Strabismus: 

• due to organic amblyopia or esotropia. 

Retinopathy 

• ‘Salt & pepper retinopathy’ resulting from non-inflammatory depigmentation of retinal pigment epithelium RPE 
• Pigmentary disturbance involve mainly posterior pole
• Some patient develop choroidal neovascularization (subretinal neovascularization) -SRNVM 
• Typical fundus picture:  
• Fine granular mottled pepper like pigment clumping of variable size.
• Affects all parts but mainly posterior pole.
• Lesion described as ‘salt pepper’ & ‘moth eaten appearance’. 

Treatment: no specific management is required.