Genetic testing for adult-onset neurodegenerative diseases: A clinical perspective

Adult-onset neurodegenerative diseases (AOND), such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and frontotemporal dementia, severely affect patients' quality of life. Pathogenic single-nucleotide variations (SNVs) and small insertions and deletions (indels) can disrupt genes involving ANOD, and expansion of short tandem repeats such as trinucleotide repeats is an important etiology of hereditary ataxia. Variations in more than one gene combined to create polygenic risk scores (PRS) for multifactorial types of AOND. Recently, genome structural variations (SVs) like copy number variations (CNVs) and expansion of long repeats are increasingly identified as the etiologies of AOND. Tools for molecular diagnosis of AOND have evolved from Sanger sequencing to next-generation sequencing (NGS) such as short-read whole-exome sequencing (WES) and whole-genome sequencing (WGS), and long-read sequencing is especially helpful in solving SVs and expansions of long repeats. Patients might have affected and/or at-risk family members at the time of diagnosis, so genetic counseling for risk handling and birth planning need to be conducted with caution. This review will help readers to better understand the genetic testing for AOND.