A small study suggests that a skin test may someday be able to diagnose Alzheimer’s and Parkinson’s diseases. Researchers have found that skin biopsies can show the high levels of abnormal proteins often associated with the two diseases. Skin and brain tissue are similar, and so researchers have looked at skin as a way to identify and diagnose the disease earlier. Currently, a definitive diagnosis of Alzheimer’s disease cannot be developed for a living person, since the only definitive way to diagnose the disease comes from examining brain tissue from a biopsy. If further developed and tested, this skin test could aide in the study and diagnosis of other neurodegenerative diseases.