Myoclonic Epilepsy With Ragged-Red Fibers Without Increased Lactate Levels

• Published in: Pediatric neurology Vol. 41; no. 1; pp. 46 - 48
• Main Authors: Kimura, Shigemi, MD, PhD, Ozasa, Shiro, MD, Nakamura, Kyoko, MD, Nomura, Keiko, MD, Kosuge, Hirofumi, MD
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.07.2009; Elsevier
• Subjects: Adolescent; Anticonvulsants - therapeutic use; Biological and medical sciences; Diagnosis, Differential; DNA Mutational Analysis; DNA, Mitochondrial; Epilepsies, Myoclonic - blood; Epilepsies, Myoclonic - complications; Epilepsies, Myoclonic - diagnosis; Epilepsies, Myoclonic - drug therapy; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Humans; Lactic Acid - blood; Male; Medical sciences; Mitochondrial Encephalomyopathies - blood; Mitochondrial Encephalomyopathies - complications; Mitochondrial Encephalomyopathies - diagnosis; Muscle, Skeletal - pathology; Mutation; Nervous system (semeiology, syndromes); Neurology; Pediatrics; Pedigree; RNA, Transfer, Lys - genetics; Lactates; Nervous system diseases; Lactic acid; Epilepsy; Central nervous system disease; Cerebral disorder
• ISSN: 0887-8994; 1873-5150
• DOI: 10.1016/j.pediatrneurol.2009.02.002

Myoclonic epilepsy associated with ragged-red fibers is one of the mitochondrial encephalomyopathies. Pathogenic mitochondrial DNA mutations have been identified in the mitochondrial transfer RNA (tRNA)Lys at positions 8344 and 8356. Characteristics of myoclonic epilepsy associated with ragged-red fibers include myoclonic epilepsy, generalized epilepsy, hearing loss, exercise intolerance, lactic acidosis, and ragged-red fibers. The elevated lactate level is one of the most important symptoms needed to make a diagnosis of mitochondrial encephalomyopathy. In the present case, however, myoclonic epilepsy was associated with ragged-red fibers but without increased lactate levels. Therefore, myoclonic epilepsy associated with ragged-red fibers should be suspected in a patient who has myoclonic epilepsy that is difficult to control with antiepileptic medications and who has other symptoms of mitochondrial disease, such as mental retardation, even if the patient's lactate level is normal.