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Nystagmus in a newborn: a manifestation of Joubert syndrome in the neonatal period. Joubert syndrome is a rare disorder, usually autosomal recessive, with a prevalence of 1:80,000 to 1:100,000. This disease presents most commonly as breathing irregularities, although the two major clinical criteria are hypotonia and developmental delay, sometimes associated with ocular movement abnormalities. The severity of the presentation varies, ranging from mild cases with normal intelligence to severe developmental delays associated with early death. We report a case of a newborn who presented to the emergency department for absent ocular fixation and torsional nystagmus without other neurological abnormalities. Her cranial MR showed cerebellar vermis agenesis and a molar tooth sign. Her laboratory evaluation, and renal and abdominal ultrasound were normal. An electroretinogram showed mixed retinal dystrophy and an AHI1 homozygous missense c.1981T>C mutation was identified (parents are carriers). Throughout infancy, she has shown mild developmental delay and hypotonia, but no respiratory abnormalities. Owing to variable expressivity, a high level of suspicion is required.