Precision medicine in neurodegenerative diseases: From research to clinical practice.

The chapter outlines how precision medicine is reshaping the way neurodegenerative diseases (NDs) which includes Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) are understood, diagnosed, and treated. It discusses the limitations of current therapies, which mainly address symptoms without altering disease progression. Genetic and molecular factors that influence disease development are described, including distinctions between familial and sporadic forms. The chapter also covers the roles of epigenetic changes, gene expression, protein dysfunction, mitochondrial DNA, and non-coding RNAs in NDs. Biomarkers in blood and cerebrospinal fluid, along with imaging techniques and digital tools, are presented as key elements in early diagnosis and disease monitoring. Patient stratification based on clinical features, molecular profiles, and biomarkers helps guide treatment decisions and improve outcomes. The chapter reviews ongoing developments in genotype-based drug design, gene therapy, pharmacogenomics, and personalized lifestyle strategies. Clinical case studies show how these approaches are being used in practice. The chapter also discusses challenges in applying precision medicine, such as trial design, data integration, unequal access, and regulatory hurdles. Finally, it highlights the future tools like single-cell transcriptomics, digital twins, and global research collaborations that aim to bring precision approaches into everyday care.