Metabolic myopathies: A guide and update for clinicians

Purpose of review: The present review will focus on the clinical features, and recent advances in the investigation and treatment, of metabolic muscle disease. The aim is to present a summary of this vast and complex topic emphasizing key points of relevance to nonspecialists in the field. Salient examples from each category will be highlighted to illustrate characteristic features and potential sources of diagnostic confusion. The general approach to management will then be outlined. Recent findings: Awareness of these diseases has grown over recent years, as has appreciation of their variable clinical presentation. Many of the precise genetic and biochemical abnormalities underlying these conditions have been elucidated and novel enzyme defects continue to be discovered. Perhaps the greatest progress, however, has been made in the management of disease. Advances in tandem mass spectrometry techniques have facilitated the introduction of nationwide neonatal screening programmes for a large number of metabolic disorders. Enzyme replacement in Pompe disease has proved successful, improving outcome in a hitherto untreatable condition. Progress towards gene therapy, perhaps the ultimate goal, has been made in animal models. Summary: Although individually rare, the metabolic myopathies together constitute a significant group of disabling and potentially life-threatening disorders. Appropriate investigations, timely treatment and genetic counselling are paramount to ameliorate the short and long-term consequences of disease.