To the Editor With interest we read the article by Martikainen et al1 about 42 genetically or biochemically confirmed adult (n = 30) and pediatric (n = 12) patients with a mitochondrial disorder (MID) who also presented with various types of an extrapyramidal movement disorder. We have the following comments and concerns.
The types of movement disorders found in this study were parkinsonism, dystonia, restless leg syndrome, tremor, and chorea.1 However, there are several other types of movement disorders, which have been occasionally described in patients with MID, such as Tourette syndrome due to mutations in the IMMP2L gene,2 tics,3 athetosis,4 dyskinesias, or progressive supranuclear ophthalmoplegia.5 Additionally, there are ballism and paroxysmal nocturnal limb movements, which have not been reported in MIDs. Were any of these other movement disorders also detected?
Finsterer J, Zarrouk-Mahjoub S. Spectrum of Movement Disorders in Mitochondrial Disorders. JAMA Neurol. 2016;73(10):1253-1254. doi:10.1001/jamaneurol.2016.2581