Published online by Cambridge University Press: 24 September 2020
Movement disorders can present a diagnostic challenge, particularly those with onset at an early age as one component of a complex neurodevelopmental disorder. With advances in next-generation sequencing technologies, the number of genes associated with movement disorders has been rapidly increasing over the last few years. Some of these genes encode transport proteins or enzymes within well-characterized metabolic pathways and their abnormal function results in disorders defined as inborn errors of metabolism (IEMs). Although individually rare, IEMs have a collective estimated incidence of 1:800 to 1:2,500 live births . Movement disorders are a common symptom in IEMs affecting the central nervous system . In general, movement disorders are not the sole symptom of these disorders, but are more often part of complex phenotypes that include other neurological and systemic signs and symptoms. The ability to recognize IEMs is crucial for clinicians evaluating patients presenting with movement disorders, as some IEMs are amenable to therapy, including specific dietary therapies or supplementation with vitamins, minerals, or cofactors that can prevent intoxication or treat deficiencies .