Muscle Channelopathies and Rhabdomyolysis

OBJECTIVEThis article describes the clinical approach to rhabdomyolysis and the diagnosis and management of episodic disorders of skeletal muscle including skeletal muscle channelopathies.LATEST DEVELOPMENTSNew gene variants that cause periodic paralysis have been identified. While these are exceedingly rare, they are now included in relevant genetic testing panels. Dantrolene is emerging as an additional option for the treatment of severe muscle stiffness, along with typical sodium channel blockers in sodium channel myotonia. Deep phenotyping in Andersen-Tawil syndrome shows significant heterogeneity with new features such as fasciculations, pain, and fatigue. A normal screening ECG is insufficient to rule out a diagnosis of Andersen-Tawil syndrome. In patients with episodic weakness, Holter monitoring is required to further investigate the possibility of Andersen-Tawil syndrome. Growth/differentiation factor-15 and fibroblast growth factor 21 serve as biomarkers of mitochondrial myopathies and can point to a mitochondrial etiology in patients with rhabdomyolysis. This article also discusses recently identified genetic abnormalities associated with rhabdomyolysis and highlights the current approach for evaluating unprovoked rhabdomyolysis.ESSENTIAL POINTSEpisodic disorders of skeletal muscles include skeletal muscle channelopathies and rhabdomyolysis. The genetic variants that underlie both disorders can also cause persistent and progressive muscle weakness. The availability and expanded use of genetic testing allow for the identification of new genes causing periodic paralysis and rhabdomyolysis. Diagnostic approaches are evolving due to easier access to and availability of genetic testing. Advances in diagnostic techniques have highlighted the lag in therapeutics for patients with these rare disorders.