This project involves the study of a novel familial neurodegenerative disorder, familial encephalopathy with neuroserpin inclusion bodies (FENIB). This disorder, which has a characteristic clinical course of progressive dementia and neurologic involvement, was initially defined in one extended family. Neuroserpin is the gene for this disorder and a mutation is present in this large kindred and four additional families/cases. This protocol will characterize the clinical phenotype, delineate the natural history of the disorder and explore genotype/phenotype correlations in the index family and possibly in other reported cases. Families with immunohistopathologically-neuroserpin positive neuronal inclusions on autopsy/biopsy in an affected member(s), neuroserpin mutation-positive proband, or with familial presenile dementia with neurologic features consistent with the original FENIB family will be enrolled.