Dysregulated expression and activity of DYRK1A, dual specificity tyrosine phosphorylation regulated kinase 1A, is a feature of several neurodevelopmental and neurodegenerative diseases, including Down syndrome, DYRK1A syndrome, autism spectrum disorders, Alzheimer's disease, and Parkinson's disease. Here, DYRK1A is linked to early-onset autosomal dominant Alzheimer disease.