A 28-year-old pregnant woman from Mumbai presents with low-grade fever, maculopapular rash on face and trunk, and mild arthralgia. Fetal ultrasound shows microcephaly. Which is the most common congenital manifestation of the viral infection responsible for this clinical presentation?

Explanation

## Congenital Manifestations of Zika Virus Infection ### Clinical Recognition The clinical triad of fever, rash, and arthralgia in a pregnant woman with fetal microcephaly is highly suggestive of **Zika virus (ZIKV) infection**. This flavivirus is the most notorious teratogenic arbovirus, particularly when maternal infection occurs in the first and second trimesters. ### Congenital Zika Syndrome (CZS) — Most Common Manifestations **Key Point:** **Microcephaly with cortical calcifications** is the hallmark and most common CNS manifestation of congenital Zika virus infection. ### Spectrum of Congenital Manifestations | Manifestation | Frequency | Timing of Infection | Imaging Features | |---------------|-----------|-------------------|------------------| | Microcephaly | Most common | 1st–2nd trimester | Cortical calcifications, ventriculomegaly | | Cortical calcifications | Very common | 1st–2nd trimester | Scattered, periventricular pattern | | Ventriculomegaly | Common | 1st–2nd trimester | Enlarged lateral ventricles | | Lissencephaly/polymicrogyria | Moderate | 1st–2nd trimester | Abnormal cortical folding | | Arthrogryposis | Less common | Early pregnancy | Joint contractures | | Eye abnormalities | Moderate | 1st–2nd trimester | Chorioretinitis, optic nerve hypoplasia | | Growth restriction | Common | Throughout | IUGR | **High-Yield:** Microcephaly with **cortical calcifications** is the pathognomonic imaging finding in congenital Zika syndrome. This distinguishes it from other causes of microcephaly (e.g., cytomegalovirus causes periventricular calcifications; toxoplasmosis causes scattered calcifications). ### Pathophysiology Zika virus crosses the placenta and directly infects neural progenitor cells, causing apoptosis and impaired neurogenesis. This results in: 1. Reduced cortical volume 2. Premature cortical calcifications (from cell death) 3. Abnormal cortical development (polymicrogyria, lissencephaly) 4. Ventriculomegaly (secondary to reduced brain mass) **Clinical Pearl:** The 2015–2016 Zika epidemic in Brazil established the causal link between ZIKV and microcephaly. Maternal infection in the first trimester carries the highest risk (10–15% of infected pregnancies result in fetal CNS abnormalities). **Mnemonic: ZIKA-CNS = Zika, Intrauterine, Knocktop (microcephaly), Apoptosis, Calcifications, Neuronal damage, Severe in 1st trimester** — captures the pathophysiology and timing.