Transient hypothyroidism associated with viral Human Parechovirus encephalitis in a newborn

• First report of Parechovirus encephalitis associated with transient hypothyroidism.
• Assessment of HpEV PCR in neonatal seizures with white matter lesions is mandatory.
• Thyroid function test is needed in a selection of newborns at risk for hypothyroidism.
• More studies are requested to reveal the link of hypothyroidism and HpEV encephalitis.

Human Parechovirus type 3 (HPeV-3) is a neurotropic virus which can cause neonatal encephalitis, presenting as encephalopathy with seizures and diffuse white matter lesions on brain imaging. Neurodevelopmental outcome is linked to the extent of white matter abnormalities. We report on a neonate with clinical and biochemical findings of transient central hypothyroidism associated with HPeV-3 encephalitis. The co-occurrence of transient hypothyroidism and viral encephalitis has not been reported in newborns before. Transient suppression of the hypothalamo–pituitary–thyroidal axis is described in critically ill babies as the nonthyroidal-illness syndrome. Assessment of thyroid function in neonatal cases of HPeV-3 infection is required to conclude whether a transient hypothyroidism as in nonthyroidal-illness syndrome may be triggered by viral meningo-encephalitis and if treatment may influence neurodevelopmental outcome.