Myoclonus in mitochondrial disorders.

TitleMyoclonus in mitochondrial disorders.
Publication TypeJournal Article
Year of Publication2014
AuthorsMancuso, M, Orsucci, D, Angelini, C, Bertini, E, Catteruccia, M, Pegoraro, E, Carelli, V, Valentino, ML, Comi, GP, Minetti, C, Bruno, C, Moggio, M, Ienco, ECaldarazzo, Mongini, T, Vercelli, L, Primiano, G, Servidei, S, Tonin, P, Scarpelli, M, Toscano, A, Musumeci, O, Moroni, I, Uziel, G, Santorelli, FM, Nesti, C, Filosto, M, Lamperti, C, Zeviani, M, Siciliano, G
JournalMov Disord
Date Published2014 May
KeywordsAdolescent, Adult, Child, Child, Preschool, Cohort Studies, Female, Humans, Italy, Male, Middle Aged, Mitochondrial Diseases, Myoclonus, Severity of Illness Index, Young Adult

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.

Alternate JournalMov. Disord.
Citation Key10.1002/mds.25839
PubMed ID24510442
Grant ListGGP07019 / / Telethon / Italy
MC_UP_1002/1 / / Medical Research Council / United Kingdom
GUP09004 / / Telethon / Italy
GTB12001 / / Telethon / Italy
GPP10005 / / Telethon / Italy