TNF‐α is a key mediator of neuroinflammation, and neuroinflammation has been associated with neurodegenerative diseases, including Parkinson's disease (PD) and Alzheimer's disease (AD).47, 48, 49 The onset of RBD is suggested to precede the development of neurodegeneration by several years.50 The frequency of RBD in these patients has not been well defined. The gene discussed is TNF; the disease is early-onset autosomal dominant Alzheimer disease.