The importance of CDO in human health is suggested by evidence for abnormal or deficient CDO activity in individuals with several autoimmune (e.g., rheumatoid arthritis) and neurodegenerative diseases (e.g., Parkinson’s and Alzheimer’s disease) ([16], [17], [37], [38], [39]). The gene discussed is CDO1; the disease is early-onset autosomal dominant Alzheimer disease.