Abstract: This document relates to methods and materials for detecting mutations that can be linked to dementia. For example, methods and materials for detecting one or more mutations within PGRN nucleic acid are provided. This document also provides methods and materials for detecting the level of progranulin expression. In addition, this document relates to methods and materials for treating mammals having a neurodegenerative disorder (e.g., dementia). For example, methods and materials for increasing PGRN polypeptide levels in mammals are provided, as are methods and materials for identifying agents that can be used to increase PGRN polypeptide levels in mammals.