Mitochondrial and Metabolic Myopathies

Bruce H. Cohen, MD, FAAN Muscle and Neuromuscular Junction Disorders p. 1732-1766 December 2019, Vol.25, No.6 doi: 10.1212/CON.0000000000000805
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PURPOSE OF REVIEW This article provides an overview of mitochondrial and metabolic biology, the genetic mechanisms causing mitochondrial diseases, the clinical features of mitochondrial diseases, lipid myopathies, and glycogen storage diseases, all with a focus on those syndromes and diseases associated with myopathy. Over the past decade, advances in genetic testing have revolutionized patient evaluation. The main goal of this review is to give the clinician the basic understanding to recognize patients at risk of these diseases using the standard history and physical examination.

RECENT FINDINGS Primary mitochondrial disease is the current designation for the illnesses resulting from genetic mutations in genes whose protein products are necessary for mitochondrial structure or function. In most circumstances, more than one organ system is involved in mitochondrial disease, and the value of the classic clinical features as originally described early in the history of mitochondrial diseases has reemerged as being important to identifying patients who may have a primary mitochondrial disease. The use of the genetic laboratory has become the most powerful tool for confirming a diagnosis, and nuances of using genetic results will be discussed in this article. Treatment for mitochondrial disease is symptomatic, with less emphasis on vitamin and supplement therapy than in the past. Clinical trials using pharmacologic agents are in progress, with the field attempting to define proper goals of treatment. Several standard accepted therapies exist for many of the metabolic myopathies.

SUMMARY Mitochondrial, lipid, and glycogen diseases are not uncommon causes of multisystem organ dysfunction, with the neurologic features, especially myopathy, occurring as a predominant feature. Early recognition requires basic knowledge of the varied clinical phenotypes before moving forward with a screening evaluation and possibly a genetic evaluation. Aside from a few specific diseases for which there are recommended interventions, treatment for the majority of these disorders remains symptomatic, with clinical trials currently in progress that will hopefully result in standard treatments.

Address correspondence to Dr Bruce H. Cohen, 215 W Bowery St, CPB 4th Fl, Akron, OH 44308, bcohen@akronchildrens.org.

RELATIONSHIP DISCLOSURE: Dr Cohen has received personal compensation as a speaker for the American Academy of Neurology and Stealth BioTherapeutics and for consulting for Mitobridge, Modis Pharmaceuticals, NeuroVive Pharmaceuticals, and Stealth BioTherapeutics. Dr Cohen has received research support from BioElectron Technology Corporation, Horizon Therapeutics, National Institutes of Health, Reata Pharmaceuticals, and Stealth BioTherapeutics. Dr Cohen has received publishing royalties from Elsevier.

UNLABELED USE OF PRODUCTS/INVESTIGATIONAL USE DISCLOSURE: Dr Cohen reports no disclosure.

© 2019 American Academy of Neurology.