We're joined once again by Dr. Karen Shackelford from BoardVitals. This week, we discuss a case about an immigrant from Central America who's pregnant.
A 26-year-old, G1P0 female is a recent immigrant from Central America and she presents with crampy abdominal pain and vaginal bleeding. By her dates, because she hasn't received prenatal care. She's of 25 weeks gestation and her past medical history is unremarkable.
She takes an over-the-counter multivitamin but no other medication. She denies alcohol, tobacco, or illicit drug use. And she spontaneously delivers a stillborn fetus.
The fetus is noted to have microcephaly and imaging performed reveals thinning of the cerebral cortices, ventriculomegaly, and subcortical calcifications.
Viral RNA is identified in both maternal and fetal body fluids. The virus is a neurotropic virus that disrupts proliferation migration and differentiation of neural precursor cells in the developing fetus.
Which of the following is the most likely pathogen?
(A) Herpex simplex virus
(B) Rubella
(C) Zeka virus
(D) Cytomegalovirus (CMV)
The pathogen here is Zeka virus. CMV is a pretty good distraction here since the question mentioned ventricular calcification. But with respect to being a neurotropic virus, Zeka is and has been in the news a lot.
It's a single-stranded RNA virus transmitted by mosquitoes. It's also related to dengue virus and the yellow fever virus.
The infection results in clinical manifestations in about 20% of people and the rest would not know they've had it. If you're infected, you're symptomatic. You have a low-grade temp. You can develop a maculopapular rash, arthralgia, and conjunctivitis.
There are other neurologic complications besides the general microcephaly. You can end up with Guillain-Barre, myelitis, meningoencephalitis, seizures, and congenital spasticity which the mother has vertically transmitted during delivery or it can be transmitted through the placenta.
It can also be sexually transmitted and through other body fluids. It can also be caused by laboratory exposure such as the transplant of infected organs. It's fairly infectious.
Pregnant women in the United States have been advised across the board to avoid travel in regions where mosquito transmission of Zeka occurs if they're going to be less than 6500 feet in altitude. This is the same thing with malaria in some parts of Kenya.
CMV is a double-stranded DNA virus. The question mentioned specifically that the virus was an RNA virus. So this would be one reason you would disqualify CMV from your correct answers.
But general CMV infection can result in chorioretinitis, hearing loss, jaundice, and periventricular calcification on imaging studies.
CMV is not associated with tropical travel or immigration.
Rubella is a single-stranded RNA virus. Congenital exposure is primarily associated with hearing loss, cataracts and congenital cardiac defects instead of neurological defects.
HSV is a double-stranded DNA virus. Congenital exposure is associated with skin lesions and obstruction of brain tissue. The candidate here can rule out HSV for no other reason than it's a DNA virus.
Zeka has been in the news a lot lately. And content gets updated on USMLE. So you should be aware of these things even if you just hear about them once or twice while you're studying. You're more likely to diagnose it than if you don't remember hearing about it at all during your studies.
"You have to be aware of what is potentially out there because you can't diagnose something you don't think of."
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