Case report: hyperkinetic movement disorder in a patient with heterozygous mutation in the GNAO1 gene

Case presentation: A male infant, cesarean term delivery. His mother had an unremarkable pregnancy. Apgar score of 8/10 and weight of 2,945 g. Newborn screening tests were normal. At 8 days of age, he presented with episodes of impaired awareness, unresponsiveness and clonus of the limbs, lasting for up to one minute. Phenobarbital was initiated, attaining full seizure control. At 6 months of age, he developed dystonia and chorea. Whole exome sequencing test was performed, which identified a heterozygous mutation in the GNAO1 gene, with substitution of Guanine to Adenine in the position chr 16:56.370.656. At 2 years of age, he presented with sporadic nocturnal dystonia episodes, preceded by nausea and vomiting. Videofluoroscopic swallowing study showed velopharyngeal insufficiency and tracheal micro-aspiration. Electroencephalogram showed spike-and-wave paroxysms and slow-wave activity in both temporo-occipital regions alternating between cerebral hemispheres. Neurological exam alterations included convergent strabismus, dystonia, chorea, hypotonia and hyporeflexia. At 4 years of age, he was admitted with status dystonicus associated with hypovolemic shock, with subsequent orotracheal intubation, sedation and transfer to a intensive care unit, where he was started on trihexyphenidyl and clobazam, with improvement and discharge after 21 days of hospitalization. Neurological exam at 6 years included global development delay, paroxistic dystonia, global hypotonia, areflexia and hypotrophy. He maintains follow-up with a multiprofessional team, using topiramate, baclofen, trihexyphenidyl and clobazam.

Discussion: The GNAO1 mutation was first described in 4 patients and was associated with early onset severe epileptic encephalopathy, although at the time there was no knowledge about other possible phenotypes. Currently, GNAO1 mutation is known to be related to a myriad of clinical presentations, which include epilepsy, neurodevelopmental delay and hyperkinetic movement disorder. The reported case exemplifies the variety of manifestations that such mutation may be correlated to. Some of its complications, such as status dystonicus, are life-threatening occurrences that require prompt recognition and treatment.

Final comments: The GNAO1 gene mutation is responsible for multiple clinical presentations. As such, it would be well advised to consider it as a differential diagnosis in patients presenting with neurodevelopmental delay, epileptic seizures and hyperkinetic movement disorders in the first year of life.

 

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Artikel online veröffentlicht:
18. September 2023