Lancet neurology
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Neurodegeneration in Parkinson's disease starts years before a clinical diagnosis can be reliably made. The prediagnostic phase of the disease offers a window of opportunity in which disease-modifying therapies-ie, those aimed at delaying or preventing the progression to overt disease and its many complications-could be most beneficial, but no such therapies are available at present. ⋯ These biomarkers will, in turn, help to identify the optimum population to be included and the most appropriate outcomes to be assessed in trials of disease-modifying drugs. Potential risks to minimally symptomatic participants, some of whom might not progress to manifest Parkinson's disease, and individuals who do not wish to know their mutation carrier status, could pose specific ethical dilemmas in the design of these trials.
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Down's syndrome is the most common genetic cause of learning difficulties, and individuals with this condition represent the largest group of people with dementia under the age of 50 years. Genetic drivers result in a high frequency of Alzheimer's pathology in these individuals, evident from neuroimaging, biomarker, and neuropathological findings, and a high incidence of cognitive decline and dementia. ⋯ Despite close similarities with late-onset Alzheimer's disease, individuals with Down's syndrome respond differently to treatment, and a targeted approach to drug development is thus necessary. Genetic and preclinical studies offer opportunities for treatment development, and potential therapies have been identified using these approaches.