A comprehensive critical review on early onset Parkinson's disease

Since its original description Parkinson's disease has been considered as a clinical condition which affects older people. Nonetheless, since late in the last century, cases starting in very young age have been described. A great controversy has arisen concerning the real pathology in these cases and, consequently, how should they be named. Early or young onset parkinsonism, early or young onset Parkinson's disease, juvenile parkinsonism, all these terms have been used indistinguishable. There have been few pathological descriptions in early onset parkinsonism. Some show striking differences from the cases of older patients but others are very similar to what has been considered classical Parkinson's disease. Younger starting age usually corresponds to greater possibility of other family members being affected. Dyskinesias and fluctuations due to chronic levodopa treatment are an early and almost invariable complication in the course of young patients. Comments on several aspects based on an extensive literature review are presented.