title: Myoclonus in mitochondrial disorders.
abstract: 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.
authors: Neurological Clinic, University of Pisa, Pisa, Italy.
authors: Michelangelo
authors: M
authors: Mancuso
authors: Daniele
authors: D
authors: Orsucci
authors: Corrado
authors: C
authors: Angelini
authors: Enrico
authors: E
authors: Bertini
authors: Michela
authors: M
authors: Catteruccia
authors: Elena
authors: E
authors: Pegoraro
authors: Valerio
authors: V
authors: Carelli
authors: Maria L
authors: ML
authors: Valentino
authors: Giacomo P
authors: GP
authors: Comi
authors: Carlo
authors: C
authors: Minetti
authors: Claudio
authors: C
authors: Bruno
authors: Maurizio
authors: M
authors: Moggio
authors: Elena Caldarazzo
authors: EC
authors: Ienco
authors: Tiziana
authors: T
authors: Mongini
authors: Liliana
authors: L
authors: Vercelli
authors: Guido
authors: G
authors: Primiano
authors: Serenella
authors: S
authors: Servidei
authors: Paola
authors: P
authors: Tonin
authors: Mauro
authors: M
authors: Scarpelli
authors: Antonio
authors: A
authors: Toscano
authors: Olimpia
authors: O
authors: Musumeci
authors: Isabella
authors: I
authors: Moroni
authors: Graziella
authors: G
authors: Uziel
authors: Filippo M
authors: FM
authors: Santorelli
authors: Claudia
authors: C
authors: Nesti
authors: Massimiliano
authors: M
authors: Filosto
authors: Costanza
authors: C
authors: Lamperti
authors: Massimo
authors: M
authors: Zeviani
authors: Gabriele
authors: G
authors: Siciliano
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D028361:Mitochondrial Diseases / Q000150:complications*; D009207:Myoclonus / Q000453:epidemiology* / Q000209:etiology*; D012720:Severity of Illness Index; D055815:Young Adult
keywords: 8344A>G; ataxia; mtDNA; myoclonic epilepsy; myoclonus