Myoclonic Epilepsy associated with Ragged Red Fibers
MERRF

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Prevalence of clinical parameters (%)







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Number of patients in the reference Percent affected patients (Between 0 and 1, eg. 0.1 = 10%)
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List of symptoms



Symptom/sign Organ system Percent affected Pubmed id Added on(yyyy-mm-dd) Edit/add reference
Myoclonus nervous 100 % 21303704 2011-10-18
Seizures nervous 100 % 21303704 2011-10-04
Myopathy skeletal 100 % 3922281 2012-01-11
Hearing loss nervous 100 % 3922281 2012-01-11
Myoclonus nervous 100 % 11850598 2011-10-04
Seizures nervous 100 % 11850598 2011-10-04
Ataxia nervous 100 % 11850598 2011-10-04
Dysarthria nervous 100 % 11850598 2011-10-04
Ataxia nervous 83 % 21303704 2011-10-04
Muscle weakness skeletal 83 % 21303704 2011-10-04
Lactate accumulation circulatory 83 % 21303704 2011-10-04
Increased blood CK skeletal 83 % 21303704 2011-10-04
Cerebral atrophy nervous 66 % 21303704 2012-07-27
Cerebellar atrophy nervous 66 % 21303704 2012-07-27
Myoclonus nervous 57 % 3922281 2012-01-11
Neuropathy nervous 50 % 21303704 2011-10-04
Myopathy skeletal 50 % 11850598 2011-10-04
Hearing loss nervous 50 % 11850598 2011-10-04
Ataxia nervous 43 % 3922281 2012-01-11
Multiple lipomas integumentary 33 % 21303704 2011-10-04
Headache nervous 33 % 21303704 2011-10-04
Vomiting digestive 33 % 21303704 2011-10-04
Dementia nervous 33 % 21303704 2011-10-04
Ptosis nervous 33 % 21303704 2011-10-04
Ophthalmoplegia nervous 33 % 21303704 2011-10-04
Lactate accumulation multi 29 % 3922281 2012-01-11
Hyperactive reflexes nervous 29 % 3922281 2012-01-11
Exercise intolerance skeletal 17 % 21303704 2011-10-04
Dementia nervous 14 % 3922281 2012-01-11
Mental retardation nervous 14 % 3922281 2012-01-11
Hypoventilation respiratory 14 % 3922281 2012-01-11
Short stature multi 14 % 3922281 2012-01-11
Dysarthria nervous 14 % 3922281 2012-01-11
Muscle weakness skeletal 14 % 3922281 2012-01-11
Babinski's sign nervous 14 % 3922281 2012-01-11
Headache nervous 14 % 3922281 2012-01-11



List of references:


MERRF: Clinical features, muscle biopsy and molecular genetics in Brazilian patients.
Paulo José Lorenzoni, Rosana H Scola, Cláudia S Kamoi Kay, Raquel C Arndt, Carlos E Silvado, Lineu C Werneck,

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.

Mitochondrion - May 2011



Maternally inherited mitochondrial myopathy and myoclonic epilepsy.
H S Rosing, L C Hopkins, D C Wallace, C M Epstein, K Weidenheim,

A family is described with familial myoclonic epilepsy associated with mitochondrial myopathy. The disorder follows a maternal inheritance pattern consistent with a mitochondrial DNA (mtDNA) mutation. The large kindred permitted exclusion of autosomal dominant, recessive, and X-linked patterns of transmission. Several characteristics of the inheritance and variability of expression within the pedigree are consistent with recently acquired knowledge about the genetics of human mtDNA. The clinical spectrum of disease is compatible with a proportionality model of mutant and wild-type mtDNAs. Muscle biopsies of affected patients showed an increased number of abnormal muscle mitochondria. Serum levels of pyruvate or pyruvate and lactate were elevated. The most severely affected patient had constant myoclonic jerking, dementia, ataxia, spasticity, hearing loss, and hypoventilation. Cerebral dysfunction in patients with mild involvement was marked by prominent photic driving seen on electroencephalograms and high-amplitude visual and somatosensory evoked responses but no myoclonus, ataxia, or dementia. The individual clinical features of the disease worsen over time for all patients; however, mildly affected patients have not become moderately affected and moderately affected patients have not become severely affected.

Annals of neurology - Mar 1985



Histochemical and molecular genetic study of MELAS and MERRF in Korean patients.
Dae Seong Kim, Dae Soo Jung, Kyu Hyun Park, In Joo Kim, Cheol Min Kim, Won Ho Lee, Soon Ki Rho,

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episode (MELAS) and myoclonic epilepsy and ragged-red fibers (MERRF) are rare disorders caused by point mutation of the tRNA gene of the mitochondrial genome. To understand the pathogenetic mechanism of MELAS and MERRF, we studied four patients. Serially sectioned frozen muscle specimens with a battery of histochemical stains were reviewed under light microscope and ultrastructural changes were observed under electron microscope. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was performed and the tRNA genes were sequenced to confirm mutations. In two patients with MELAS, strongly succinyl dehydrogenase positive blood vessels (SSVs) and many cytochrome oxidase (COX) positive ragged-red fibers (RRFs) were observed, and A3243G mutations were found from the muscle samples. In two patients with MERRF, neither SSV nor COX positive RRFs were seen and A8344G mutations were found from both muscle and blood samples. In the two MERRF families, the identical mutation was observed among family members. The failure to detect the mutation in blood samples of the MELAS suggests a low mutant load in blood cells. The histochemical methods including COX stain are useful for the confirmation and differentiation of mitochondrial diseases. Also, molecular biological study using muscle sample seems essential for the confirmation of the mtDNA mutation.

Journal of Korean medical science - Feb 2002