Delayed recognition of Joubert syndrome in a child initially diagnosed with autism spectrum disorder without intellectual impairment.

Joubert syndrome (JS) is a rare ciliopathy characterised by the molar tooth sign on brain MRI, cerebellar vermis hypoplasia, hypotonia and developmental delay. We report an elementary school-aged boy initially diagnosed with autism spectrum disorder without intellectual impairment because of early language delay, social communication difficulties and stereotyped behaviours. Developmental screening at 4 years of age using the Denver Developmental Screening Test II demonstrated delays in language and social communication domains. At presentation to our clinic at 8 years of age, cognitive evaluation with Wechsler Intelligence Scale for Children-Revised (WISC-R) demonstrated normal intellectual functioning (Full Scale IQ=98). The patient had mild axial hypotonia in infancy, a normal head circumference (50th-75th percentile) and later developed gait ataxia with oculomotor apraxia at 8 years of age. The first brain MRI performed at 4 years of age at an outside institution was reported as normal, whereas repeat MRI at 8 years of age demonstrated the molar tooth sign and cerebellar vermis hypoplasia.5 6 Genetic testing identified variants in ciliopathy-related genes. This case highlights that JS may present with preserved cognition and subtle early neuroimaging findings, emphasising the importance of repeating neuroimaging and comprehensive genetic evaluation when new cerebellar signs emerge.