Infectious Disease · Congenital Infections
The facts most likely to be tested
Congenital Zika virus infection is characterized by severe microcephaly with a collapsed skull and redundant scalp skin.
The virus exhibits neurotropism, specifically targeting neural progenitor cells and leading to cortical thinning and subcortical calcifications.
Affected infants frequently present with arthrogryposis (joint contractures) due to lower motor neuron involvement or in utero immobility.
Ocular findings are highly specific and include macular scarring, focal pigmentary mottling, and optic nerve hypoplasia.
Transmission occurs primarily via the bite of an infected Aedes aegypti mosquito, but sexual transmission and vertical transmission are well-documented.
Diagnosis is confirmed via Zika virus RNA detection in serum, urine, or cerebrospinal fluid using reverse transcription-polymerase chain reaction (RT-PCR).
There is no specific antiviral treatment or vaccine for Zika virus, making vector control and avoidance of travel to endemic areas the primary prevention strategies.
Vignette unlocked
A 2-day-old male infant is born to a mother who traveled to Brazil during her second trimester. Physical examination reveals a head circumference below the 3rd percentile for gestational age. The infant has a collapsed skull with redundant scalp skin and bilateral clubfoot deformities. Funduscopic examination demonstrates macular scarring and pigmentary mottling. A head ultrasound reveals subcortical calcifications and ventriculomegaly.
What is the most likely etiology of this infant's clinical presentation?
Congenital Zika virus infection
The combination of severe microcephaly, redundant scalp skin, arthrogryposis, and specific ocular findings (macular scarring) is pathognomonic for congenital Zika virus infection, which is confirmed via RT-PCR.
Full handout
High yield triage
Etiology / Epidemiology
Transmitted via Aedes mosquito or sexual contact; vertical transmission to fetus during pregnancy.
Clinical Manifestations
Classic congenital Zika syndrome features severe microcephaly and intracranial calcifications.
Diagnosis
RT-PCR of maternal/fetal serum or urine is the gold standard for acute infection.
Treatment
No specific antiviral; supportive care is the only management. Avoid NSAIDs until dengue is ruled out.
Prognosis
High risk of neurodevelopmental delay and seizures; long-term multidisciplinary follow-up required.
Full handout
Epidemiology & Etiology
Zika is a flavivirus primarily transmitted by the Aedes aegypti mosquito. Vertical transmission occurs during any trimester, though first-trimester infection carries the highest risk of congenital malformations. Travel to endemic regions in the Americas and Southeast Asia is the primary risk factor.
Pertinent Anatomy
The virus exhibits neurotropism, specifically targeting fetal neural progenitor cells. This leads to destruction of the developing cerebral cortex and subsequent microcephaly.
Pathophysiology
The virus crosses the placenta and induces apoptosis of neural stem cells. This results in cortical thinning, subcortical calcifications, and secondary ventriculomegaly. The resulting brain architecture is often described as simplified gyral pattern.
Clinical Manifestations
Infants present with severe microcephaly (head circumference <3rd percentile) and a collapsed skull appearance. Key findings include intracranial calcifications (often at the gray-white matter junction), ocular abnormalities (macular scarring), and arthrogryposis (joint contractures). Red flags include hypertonia, irritability, and intractable seizures.
Diagnosis
The gold standard is RT-PCR for viral RNA in serum or urine. Serologic testing for Zika IgM is used if PCR is negative, but cross-reactivity with other flaviviruses (e.g., Dengue) is common. Fetal ultrasound may show intracranial calcifications or microcephaly as early as 18-20 weeks gestation.
Treatment
Management is strictly supportive care focusing on physical therapy and seizure control. Avoid NSAIDs (e.g., aspirin, ibuprofen) in the neonate until dengue fever is excluded due to the risk of hemorrhage. Early intervention services are mandatory for neurodevelopmental support.
Prognosis
Prognosis is poor for infants with symptomatic congenital Zika syndrome. Key complications include permanent intellectual disability, epilepsy, and motor impairment. Patients require lifelong multidisciplinary monitoring by neurology, ophthalmology, and physical medicine.
Differential Diagnosis
Cytomegalovirus (CMV): periventricular calcifications
Toxoplasmosis: diffuse intracranial calcifications
Rubella: associated with cataracts and PDA
Chikungunya: typically presents with acute fever/rash, not microcephaly
Dengue: lacks the specific neurodevelopmental malformations of Zika