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MERRF : Synonym: Myoclonic Epilepsy Associated with Ragged Red Fibers
Velez-Bartolomei F, Lee C, Enns G
GeneReviews® [Internet], 2021
Revue : GeneReviews® [Internet] Titre : MERRF : Synonym: Myoclonic Epilepsy Associated with Ragged Red Fibers Type de document : Article Auteurs : Velez-Bartolomei F ; Lee C ; Enns G Année de publication : 07/01/2021 Langues : Anglais (eng) Mots-clés : article de synthèse ; classification des maladies ; conseil génétique ; corrélation génotype-phénotype ; description de la maladie ; diagnostic ; diagnostic différentiel ; MERRF ; myopathie mitochondriale ; prévalence ; prise en charge thérapeutique Résumé : Initial Posting: June 3, 2003; Last Update: January 7, 2021.
Clinical characteristics.
MERRF (myoclonic epilepsy with ragged red fibers) is a multisystem disorder characterized by myoclonus (often the first symptom) followed by generalized epilepsy, ataxia, weakness, exercise intolerance, and dementia. Onset can occur from childhood to adulthood, occurring after normal early development. Common findings are ptosis, hearing loss, short stature, optic atrophy, cardiomyopathy, cardiac dysrhythmias such as Wolff-Parkinson-White syndrome, and peripheral neuropathy. Pigmentary retinopathy, optic neuropathy, diabetes mellitus, and lipomatosis have been observed.
Diagnosis/testing.
A clinical diagnosis of MERRF can be established in a proband with the following four "canonic" features: myoclonus, generalized epilepsy, ataxia, and ragged red fibers (RRF) in the muscle biopsy. A molecular diagnosis is established in a proband with suggestive findings and a pathogenic variant in one of the genes associated with MERRF. The m.8344A>G pathogenic variant in the mitochondrial gene MT-TK is present in more than 80% of affected individuals with typical findings. Pathogenic variants in MT-TF, MT-TH, MT-TI, MT-TL1, MT-TP, MT-TS1, and MT-TS2 have also been described in a subset of individuals with MERRF.
Management.
Treatment of manifestations: Ubiquinol, carnitine, alpha lipoic acid, vitamin E, vitamin B complex, and creatine may be of benefit to some individuals; traditional anticonvulsant therapy per neurologist for seizures; levetiracetam or clonazepam for myoclonus; physical therapy to improve any impaired motor function; aerobic exercise; standard pharmacologic therapy for cardiac symptoms; hearing aids or cochlear implants for hearing loss; diabetes mellitus treatment per endocrinologist.
Prevention of primary manifestations: Coenzyme Q10 (50-200 mg 2-3x/day), L-carnitine (1000 mg 2-3x/day), alpha lipoic acid, vitamin E, vitamin B supplements, and creatine, often used to improve mitochondrial function, have been of modest benefit in some individuals. Doses for children should be adjusted appropriately.
Surveillance: Routine evaluations every six to 12 months initially; annual neurologic, ophthalmologic, cardiology (electrocardiogram and echocardiogram), and endocrinologic evaluations (fasting blood sugar and TSH); audiology evaluations every two to three years.
Agents/circumstances to avoid: Mitochondrial toxins (e.g., aminoglycoside antibiotics, linezolid, cigarettes, alcohol); valproic acid should be avoided in the treatment of seizures.
Pregnancy management: During pregnancy, affected or at-risk women should be monitored for diabetes mellitus and respiratory insufficiency, which may require therapeutic interventions.
Genetic counseling.
MERRF is caused by pathogenic variants in mtDNA and is transmitted by maternal inheritance. The father of a proband is not at risk of having the mtDNA pathogenic variant. The mother of a proband usually has the mtDNA pathogenic variant and may or may not have symptoms. A male with a mtDNA pathogenic variant cannot transmit the pathogenic variant to any of his offspring. A female with a mtDNA pathogenic variant (whether symptomatic or asymptomatic) transmits the pathogenic variant to all of her offspring. Prenatal testing and preimplantation genetic testing for MERRF are possible if a mtDNA pathogenic variant has been detected in the mother. However, because the mutational load in embryonic and fetal tissues sampled (i.e., amniocytes and chorionic villi) may not correspond to that of all fetal tissues and because the mutational load in tissues sampled prenatally may shift in utero or after birth as a result of random mitotic segregation, prediction of the phenotype from prenatal studies is not possible.Lien associé : Texte complet disponible en accès libre sur Bookshelf GeneReviews® Pubmed / DOI : Pubmed : 20301693 Avis des lecteurs Aucun avis, ajoutez le vôtre !
(mauvais) 15 (excellent)
Revue : StatPearls [Internet] Titre : Congenital Myotonic Dystrophy Type de document : Article Auteurs : Jain A ; Al Khalili Y Année de publication : 15/12/2020 Langues : Anglais (eng) Mots-clés : article de synthèse ; complication de la maladie ; description de la maladie ; diagnostic ; diagnostic différentiel ; dystrophie myotonique ; dystrophie myotonique de type 1 ; éducation thérapeutique du patient ; épidémiologie ; essai clinique ; incidence ; maladie neuromusculaire ; physiopathologie ; prévalence ; prise en charge thérapeutique ; pronostic Lien associé : Texte complet disponible en accès libre sur Bookshelf StatPearls Pubmed / DOI : Pubmed : 32809353 Avis des lecteurs Aucun avis, ajoutez le vôtre !
(mauvais) 15 (excellent)
Revue : StatPearls [Internet] Titre : Facioscapulohumeral Muscular Dystrophy Type de document : Article Auteurs : Fecek C ; Emmady PD Editeur : Treasure Island (FL) Année de publication : 12/12/2020 Langues : Anglais (eng) Mots-clés : article de synthèse ; complication de la maladie ; description de la maladie ; diagnostic ; diagnostic différentiel ; dystrophie musculaire ; dystrophie musculaire facio-scapulo-humérale ; éducation thérapeutique du patient ; épidémiologie ; maladie neuromusculaire ; prévalence ; prise en charge thérapeutique ; pronostic Lien associé : Texte complet disponible en accès libre sur Bookshelf StatPearls Pubmed / DOI : Pubmed : 32644454 En ligne : http://www.ncbi.nlm.nih.gov/pubmed/32644454 Avis des lecteurs Aucun avis, ajoutez le vôtre !
(mauvais) 15 (excellent)
Revue : StatPearls [Internet] Titre : Werdnig Hoffmann Disease Type de document : Article Auteurs : Emmady PD ; Bodle J Editeur : Treasure Island (FL) Année de publication : 12/12/2020 Langues : Anglais (eng) Mots-clés : amyotrophie spinale ; amyotrophie spinale proximale (type I) ; article de synthèse ; complication de la maladie ; description de la maladie ; diagnostic ; diagnostic différentiel ; éducation thérapeutique du patient ; épidémiologie ; maladie du motoneurone ; maladie neuromusculaire ; physiopathologie ; prévalence ; prise en charge thérapeutique ; pronostic Lien associé : Texte complet disponible en accès libre sur Bookshelf StatPearls Pubmed / DOI : Pubmed : 32644359 En ligne : http://www.ncbi.nlm.nih.gov/pubmed/32644359 Avis des lecteurs Aucun avis, ajoutez le vôtre !
(mauvais) 15 (excellent)
Revue : GeneReviews® [Internet] Titre : Spinal Muscular Atrophy Type de document : Article Auteurs : Prior TW ; Leach ME ; Finanger E Année de publication : 3/12/2020 Langues : Anglais (eng) Mots-clés : amyotrophie spinale ; amyotrophie spinale proximale (type 0) ; amyotrophie spinale proximale (type I) ; amyotrophie spinale proximale (type II) ; amyotrophie spinale proximale adulte (type IV) ; amyotrophie spinale proximale liée à SMN1 ; amyotrophie spinale proximale type 3 ; article de synthèse ; classification des maladies ; conseil génétique ; corrélation génotype-phénotype ; description de la maladie ; diagnostic ; diagnostic différentiel ; diagnostic moléculaire ; épidémiologie ; maladie du motoneurone ; maladie neuromusculaire ; prévalence ; prise en charge thérapeutique Résumé : Initial Posting: February 24, 2000; Last Revision: December 3, 2020.
Clinical characteristics.
Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adulthood. The weakness is symmetric, proximal > distal, and progressive. Before the genetic basis of SMA was understood, it was classified into clinical subtypes based on maximum motor function achieved; however, it is now apparent that the phenotype of SMN1-associated SMA spans a continuum without clear delineation of subtypes. With supportive care only, poor weight gain with growth failure, restrictive lung disease, scoliosis, and joint contractures are common complications; however, newly available targeted treatment options are changing the natural history of this disease.
Diagnosis/testing.
The diagnosis of SMA is established in a proband with a history of motor difficulties or regression, proximal muscle weakness, reduced/absent deep tendon reflexes, evidence of motor unit disease, AND/OR by the identification of biallelic pathogenic variants in SMN1 on molecular genetic testing. Increases in SMN2 copy number often modify the phenotype.
Management.
Treatment of manifestations: Therapies targeted to the underlying disease mechanism include nusinersen (Spinraza®; an antisense oligonucleotide) for the treatment of all types of SMA and onasemnogene abeparvovec-xioi (Zolgensma®; gene replacement therapy) for the treatment of type I SMA. These targeted treatments may prevent the development or slow the progression of some features of SMA; efficacy is improved when treatment is initiated before symptom onset. It is unclear what the long-term effect of these treatments will be or if new phenotypes will arise in treated individuals.
Proactive supportive treatment by a multidisciplinary team is essential to reduce symptom severity, particularly in the most severe cases of SMA. When nutrition or dysphagia is a concern, placement of a gastrostomy tube early in the course of the disease is appropriate. Standard therapy for gastroesophageal reflux disease and chronic constipation. Formal consultation and frequent follow up with a pulmonologist familiar with SMA is necessary. As respiratory function deteriorates, tracheotomy or noninvasive respiratory support may be offered. Surgical repair for scoliosis should be considered based on progression of the curvature, pulmonary function, and bone maturity. Surgical intervention for hip dislocation for those with pain.
Surveillance: Presymptomatic individuals require monitoring for the development of symptoms to determine appropriate timing to initiate targeted and/or supportive therapies. Multidisciplinary evaluation every six months or more frequently for weaker children is indicated to assess nutritional state, respiratory function, motor function, and orthopedic status, and to determine appropriate interventions.
Agents/circumstances to avoid: Prolonged fasting, particularly in the acutely ill infant with SMA.
Evaluation of relatives at risk: It is appropriate to determine the genetic status of younger, apparently asymptomatic sibs of an affected individual in order to identify as early as possible those who would benefit from prompt initiation of targeted treatment.
Genetic counseling.
SMA is inherited in an autosomal recessive manner. Each pregnancy of a couple who have had a child with SMA has an approximately 25% chance of producing an affected child, an approximately 50% chance of producing an asymptomatic carrier, and an approximately 25% chance of producing an unaffected child who is not a carrier. These recurrence risks deviate slightly from the norm for autosomal recessive inheritance because about 2% of affected individuals have a de novo SMN1 variant on one allele; in these instances, only one parent is a carrier of an SMN1 variant, and thus the sibs are not at increased risk for SMA. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the diagnosis of SMA has been confirmed by molecular genetic testing in an affected family member.Lien associé : Texte complet disponible en accès libre sur Bookshelf GeneReviews® Pubmed / DOI : Pubmed : 20301526 Avis des lecteurs Aucun avis, ajoutez le vôtre !
(mauvais) 15 (excellent)
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GeneReviews® [Internet], 2020
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