Metabolic myopathies are rare inherited disorders that deserve more attention from neurologists and pediatricians. Pompe disease and McArdle disease represent some of the most common diseases in clinical practice; however, other less common diseases are now better-known. In general the pathophysiology of metabolic myopathies needs to be better understood. Thanks to the advent of next-generation sequencing (NGS), genetic testing has replaced more invasive investigations and sophisticated enzymatic assays to reach a final diagnosis in many cases. The current diagnostic algorithms for metabolic myopathies have integrated this paradigm shift and restrict invasive investigations for complicated cases. Moreover, NGS contributes to the discovery of novel genes and proteins, providing new insights into muscle metabolism and pathophysiology. More importantly, a growing number of these conditions are amenable to therapeutic approaches such as diets of different kinds, exercise training protocols, and enzyme replacement therapy or gene therapy. Prevention and management—notably of rhabdomyolysis—are key to avoiding serious and potentially life-threatening complications and improving patients’ quality of life. Although not devoid of limitations, the newborn screening programs that are currently mushrooming across the globe show that early intervention in metabolic myopathies is a key factor for better therapeutic efficacy and long-term prognosis. As a whole NGS has largely increased the diagnostic yield of metabolic myopathies, but more invasive but classical investigations are still critical when the genetic diagnosis is unclear or when it comes to optimizing the follow-up and care of these muscular disorders.

Les myopathies congénitales constituent un ensemble hétérogène de maladies neuromusculaires aussi bien sur le plan clinique que génétique. Le séquençage à haut débit, ciblé ou non, couplé à l’analyse de la biopsie musculaire, facilite grandement leur caractérisation précise et conduisent parfois à des découvertes inattendues comme dans le cas rapporté ci-dessous d’une famille koweitienne en errance diagnostique depuis de nombreuses années.

Médecine/sciences (M/S), revue internationale dans le domaine de la recherche biologique, médicale et en santé

Le syndrome de Schwartz-Jampel (SJS, OMIM #255800) est une affection génétique ultra-rare définie par des manifestations myotoniques et des anomalies ostéo-articulaires. Transmis selon un mode autosomique récessif, sa prévalence est plus élevée dans les zones de forte endogamie. La découverte du gène HSPG2 codant une protéine de la lame basale a permis de mieux en délimiter les contours nosologiques. Le diagnostic est généralement très fortement suspecté cliniquement puis confirmé en biologie moléculaire. Le traitement reste à ce jour essentiellement symptomatique. The Schwartz-Jampel syndrome (SJS, OMIM #255800) is an ultra-rare genetic disease characterized by myotonic manifestations combined with bone and cartilage abnormalities. Following an autosomal recessive mode of inheritance, its prevalence is more significant in highly-inbred areas. The unraveling of the HSPG2 gene encoding a protein of the basal lamina enabled a better nosological delineation of the syndrome. The diagnosis is usually strongly suspected at the clinical level and then confirmed by molecular biology. To date, the treatment remains essentially symptomatic.