To describe the case of a 17-year-old developmentally delayed male presenting with two years of asymmetric tremor and gait impairment.

The patient was born at 38 weeks with macrocephaly. He had significant motor and language developmental delay. At age 15 he developed a new jerky left arm and head tremor that progressed to his left leg. His left foot turned inward; foot drag impaired his gait with frequent falls. Symptoms progressed and are now constant without clear triggers or variation. There was no benefit from anti-psychotic discontinuation or trials of levodopa, trihexyphenidyl, propranolol, clonidine or baclofen. There is no significant family history.

Workup was negative for electrolyte abnormalities, Wilson’s disease, inborn errors of metabolism and mitochondrial disease. MRI Brain showed Molar Tooth Sign: elongated superior cerebellar peduncles and vermian hypoplasia. Genetic testing revealed a de novo 3.7Mb  interstitial deletion of 32 protein-coding genes. Two deleted genes, SUFU and ARL3, are implicated in Joubert Syndrome (JS). SUFU cases are phenotypically similar (facial dysmorphisms, intellectual disability, ataxic gait), though without tremor.

This is the first report of the unique phenotype of a late-onset asymmetric dystonic-ataxic tremor in an individual with imaging and genetics indicative of JS, adding to the syndrome’s phenotypically and genetically heterogeneous spectrum.