Spectrum of Movement Disorders in Mitochondrial Disorders–Reply

In Reply Finsterer and Zarrouk-Mahjoub list movement disorders not mentioned in our article¹; however, we would question their relevance. The article they referenced by Gimelli et al² reports 4 cases of inherited Tourette syndrome. Although the protein localizes to mitochondria, no evidence of mitochondrial dysfunction suggestive of an oxidative phosphorylation defect is provided; indeed, we are not aware of any definite Tourette syndrome cases related to primary mitochondrial disorders. The other article they referenced by van Rossum and ten Houten³ describes a patient with the m.3243A>G mutation and tics that “consisted of blinking of the eyes, movement [of] the head and the rubbing of the chin along the shoulder,” features suggesting seizure semiology rather than a tic disorder, particularly given the high prevalence of epilepsy in this genotype⁴ and that the patient had documented epilepsy.