Funding agencies: This work was funded by Telethon (grant no.: GUP09004). The work of the “Besta” group of Milan was supported by the Pierfranco and Luisa Mariani Foundation Italy, Ricerca 2000, Fondazione Giuseppe Tomasello ONLUS, and Fondazione Telethon-Italy (grant nos.: GGP07019 and GPP10005). The work of the group of the University of Milan was supported by Associazione Amici del Centro Dino Ferrari, by the Telethon project GTB07001ER, and by a Telethon grant “Network of Genetic Biobanks” (no.: GTB07001).
Myoclonus in mitochondrial disorders
Article first published online: 7 FEB 2014
© 2014 International Parkinson and Movement Disorder Society
Volume 29, Issue 6, pages 722–728, May 2014
How to Cite
Mancuso, M., Orsucci, D., Angelini, C., Bertini, E., Catteruccia, M., Pegoraro, E., Carelli, V., Valentino, M. L., Comi, G. P., Minetti, C., Bruno, C., Moggio, M., Ienco, E. C., Mongini, T., Vercelli, L., Primiano, G., Servidei, S., Tonin, P., Scarpelli, M., Toscano, A., Musumeci, O., Moroni, I., Uziel, G., Santorelli, F. M., Nesti, C., Filosto, M., Lamperti, C., Zeviani, M. and Siciliano, G. (2014), Myoclonus in mitochondrial disorders. Mov. Disord., 29: 722–728. doi: 10.1002/mds.25839
Relevant conflicts of interest/financial disclosures: Nothing to report.
Full financial disclosures and author roles may be found in the online version of this article.
- Issue published online: 6 MAY 2014
- Article first published online: 7 FEB 2014
- Manuscript Accepted: 17 JAN 2014
- Manuscript Revised: 8 JAN 2014
- Manuscript Received: 22 JUL 2013
- myoclonic epilepsy;
Myoclonus is a possible manifestation of mitochondrial disorders, and its presence is considered, in association with epilepsy and the ragged red fibers, pivotal for the syndromic diagnosis of MERRF (myoclonic epilepsy with ragged red fibers). However, its prevalence in mitochondrial diseases is not known. The aims of this study are the evaluation of the prevalence of myoclonus in a big cohort of mitochondrial patients and the clinical characterization of these subjects. Based on the database of the “Nation-wide Italian Collaborative Network of Mitochondrial Diseases,” we reviewed the clinical and molecular data of mitochondrial patients with myoclonus among their clinical features. Myoclonus is a rather uncommon clinical feature of mitochondrial diseases (3.6% of 1,086 patients registered in our database). It is not strictly linked to a specific genotype or phenotype, and only 1 of 3 patients with MERRF harbors the 8344A>G mutation (frequently labeled as “the MERRF mutation”). Finally, myoclonus is not inextricably linked to epilepsy in MERRF patients, but more to cerebellar ataxia. In a myoclonic patient, evidences of mitochondrial dysfunction must be investigated, even though myoclonus is not a common sign of mitochondriopathy. Clinical, histological, and biochemical data may predict the finding of a mitochondrial or nuclear DNA mutation. Finally, this study reinforces the notion that myoclonus is not inextricably linked to epilepsy in MERRF patients, and therefore the term “myoclonic epilepsy” seems inadequate and potentially misleading. © 2014 International Parkinson and Movement Disorder Society