Early-onset Parkinson's disease is a rare parkinsonian disorder that typically begins between the ages of 21-45. It is characterized by symptoms such as rigidity, painful cramps, tremors, bradykinesia, dystonia, gait issues, falls, and other non-motor symptoms. The disease progresses slowly and shows a more significant response to dopaminergic therapy compared to typical Parkinson's disease. It is considered a genetic disorder, with motor symptoms appearing earlier than usual, often before the age of 50.