Juvenile parkinsonism: Differential diagnosis, genetics, and treatment.

Juvenile parkinsonism is arbitrarily defined as parkinsonian symptoms and signs presenting prior to 21 years of age. Levodopa-responsive juvenile parkinsonism that is consistent with diagnostic criteria for Parkinson's disease is most often caused by mutations in the PARK-Parkin, PARK-PINK1, or PARK-DJ1 genes. However, many other genetic and acquired parkinsonian disorders presenting in childhood or young adulthood are being reported, often with atypical features, such as presence of other movement disorders, cognitive decline, and psychiatric symptoms. The genetic landscape of juvenile parkinsonism is rapidly changing with the discovery of new genes. Although the mainstay of treatment remains levodopa, other symptomatic therapies such as botulinum toxin for focal dystonia, supportive medical therapies, and deep brain stimulation in select cases, may also be used to provide the most optimal long-term outcomes. Since the topic has not been reviewed recently, we aim to provide an update on genetics, differential diagnosis, evaluation, and treatment of juvenile parkinsonism.