Dystonia with aphonia, slow horizontal saccades, epilepsy and photic myoclonus: A novel syndrome?

Background: Dystonia with anarthria and/or aphonia is a rare syndromic association. Here we present two cases with slowly progressive, severe generalized dystonia and aphonia, slow horizontal saccades, epilepsy and photic myoclonus. Methods: Detailed clinical data were collected over two decades in the female (index) patient and for nine years in her similarly affected son. Sanger sequencing followed by exome sequencing was performed. Results: Both patients had leg onset generalized dystonia with gradual rostral spread including prominent facial and oro-mandibular involvement. The index patient was anarthric, her son aphonic. Both had saccadic slowing, more marked for the horizontal plane, and subclinical epileptic activity. The index patient also had photic myoclonus and a combined axonal and demyelinating neuropathy. Known genetic causes of similar syndromes were not identified. Conclusion: These cases with caudo-rostrally spreading generalized dystonia with prominent facial and oro-mandibular involvement, severe speech impairment, marked slowing of horizontal saccades, and photic myoclonus likely represent a novel entity.