Alzheimer Disease–like Phenotype Associated With the c.154delA Mutation in Progranulin

Abstract

OBJECTIVE: To characterize a kindred with a familial neurodegenerative disorder associated with a mutation in progranulin (PGRN), with emphasis on the unique clinical features in this kindred. DESIGN: Antemortem and postmortem characterization of a kindred with a familial neurodegenerative disorder. SETTING: Multispecialty group academic medical center. PATIENTS: Affected members of a kindred with dementia with or without parkinsonism associated with a unique mutation in PGRN. MAIN OUTCOME MEASURE: Genotype-phenotype correlation. RESULTS: Of 10 affected individuals identified, 6 presented with early amnestic symptoms which resulted in initial diagnoses of Alzheimer disease or amnestic mild cognitive impairment. Some individuals presented with features characteristic of frontotemporal dementia. Mean age at onset was substantially younger in generation III (75.8 years; range, 69-80 years) than in generation II (60.7 years; range, 55-66 years). The pattern of cerebral atrophy varied widely in the affected individuals. Neuropathologic features in 6 individuals included frontotemporal lobar degeneration with ubiquitin-positive neuronal cytoplasmic and intranuclear inclusions (FTLD-U with NII). PGRN analysis revealed a single base pair deletion in exon 2 (c.154delA), which caused a frameshift (p.Thr52HisfsX2) and, therefore, creation of a premature termination codon and a likely null allele. CONCLUSIONS: In this large kindred, most affected individuals had clinical presentations that resembled Alzheimer disease or amnestic mild cognitive impairment associated with a mutation in PGRN and underlying FTLD-U with NII neuropathologic abnormalities. This finding is in distinct contrast to previously reported kindreds, in which clinical presentations have typically been within the spectrum of FTLD. The basis for the large difference in age at onset between generations requires further study.