title: MERRF: Clinical features, muscle biopsy and molecular genetics in Brazilian patients.
abstract: Myoclonic epilepsy with ragged red fibers (MERRF) is a mitochondrial disease that is characterized by myoclonic epilepsy with ragged red fibers (RRF) in muscle biopsies. The aim of this study was to analyze Brazilian patients with MERRF. Six patients with MERRF were studied and correlations between clinical findings, laboratory data, electrophysiology, histology and molecular features were examined. We found that blood lactate was increased in four patients. Electroencephalogram studies revealed generalized epileptiform discharges in five patients and generalized photoparoxysmal responses during intermittent photic stimulation in two patients. Muscle biopsies showed RRF in all patients using modified Gomori-trichrome and succinate dehydrogenase stains. Cytochrome c oxidase (COX) stain analysis indicated deficient activity in five patients and subsarcolemmal accumulation in one patient. Molecular analysis of the tRNA(Lys) gene with PCR/RFLP and direct sequencing showed the A8344G mutation of mtDNA in five patients. The presence of RRFs and COX deficiencies in muscle biopsies often confirmed the MERRF diagnosis. We conclude that molecular analysis of the tRNA(Lys) gene is an important criterion to help confirm the MERRF diagnosis. Furthermore, based on the findings of this study, we suggest a revision of the main characteristics of this disease.
authors.affiliation: Neurology Division, Department of Internal Medicine, Universidade Federal do Paraná, Curitiba, PR, Brazil.
authors.forename: Paulo José
authors.initials: PJ
authors.lastname: Lorenzoni
authors.forename: Rosana H
authors.initials: RH
authors.lastname: Scola
authors.forename: Cláudia S Kamoi
authors.initials: CS
authors.lastname: Kay
authors.forename: Raquel C
authors.initials: RC
authors.lastname: Arndt
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Silvado
authors.forename: Lineu C
authors.initials: LC
authors.lastname: Werneck
mesh_terms: D000328:Adult; D001706:Biopsy; D001774:Blood Chemical Analysis; D001938:Brazil; D004272:DNA, Mitochondrial / Q000235:genetics; D004569:Electroencephalography; D003576:Electron Transport Complex IV / Q000032:analysis; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D017243:MERRF Syndrome / Q000235:genetics / Q000473:pathology; D008297:Male; D008853:Microscopy; D008875:Middle Aged; D009132:Muscles / Q000473:pathology* / Q000503:physiopathology*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012357:RNA, Transfer, Lys / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D012357:RNA, Transfer, Lys; D003576:Electron Transport Complex IV