CMV infection

 
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Medical Sciences Department, Pediatric Oncall

Address for Correspondence: Dr Ira Shah, 1, B Saguna, 271, B St Francis Road, Vile Parle {W}, Mumbai 400056.


Clinical Problem :
Case Report: - A pregnant woman at 8 months gestation underwent a regular antenatal ultrasound where it was found that the fetus had mild ventriculomegaly. She then underwent a malformation scan and it was found that the child had Dandy Walker variant with subependymal calcifications in the brain with normal abdominal scan. The mother had fever at 3 months of gestation. A TORCH titre was done in the mother and CMV IgG was positive with absent CMV IgM. Karyotype was not advised as there were no other abnormal features.


Question :
What should be further management_?

Expert Opinion :
Prenatal diagnosis of CMV is difficult and complicated. The mother is CMV IgG positive suggesting that she had CMV in the past. However it does not tell us whether she had CMV in the recent past or earlier, one way to know is to repeat CMV IgG after 4 weeks and see for 4 fold rise or by doing the CMV IgG avidity test. 4 fold rise is suggestive of recent infection whereas same titre or mildly elevated, decreased time is suggestive of past CMV infection. Measurement of CMV-specific IgG avidity has proven to be a powerful tool for distinguishing primary from nonprimary CMV infection. Defined as the strength with which the IgG attaches to antigen, IgG avidity matures with the length of time following primary infection. Thus, IgG produced within the first few months following primary infection exhibits low avidity, whereas IgG produced several months or years later exhibits high avidity. Several groups of investigators have shown that detection of CMV specific IgG of low avidity is a reliable indicator of infection within the previous 6-8 months.
What is important is to know whether the fetus is infected with CMV infection. Spread of CMV infection to the fetus occurs with placental infection. Once fetal infection occurs, the virus replicates in the renal tubular epithelium, passes into urine and amniotic fluid. Hence amniocentesis or percutaneous umbilical blood sampling can be done for isolating virus by PCR or CMV IgM. However this is possible only after 32 weeks of gestation. This is because of necessary time interval from maternal infection through transmission, fetal infection and viral shedding. The amniotic fluid is most likely to be positive if tested 7 weeks or more after the maternal infection. However, doing these procedures are fraught with risk and there are currently no well-studied, effective therapies for CMV in pregnancy. Intravenous ganciclovir injection in fetus has been tried but response was not good. Thus, here since the pregnancy is already is 8th months of gestation, one can wait till the mother delivers, monitor the child for signs and laboratory features of CMV infection and then treat accordingly. Also, other system involvement can be checked for and if any dysmorphism, then even karyotype can be done.

E-published: 1st February 2010 Vol 7 Issue 2 Art No 12


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