Hypokinesia and presenile dementia in a Dutch family with a novel insertion in the prion protein gene.

The clinical features and disease course of six patients from a family with autosomal dominant inheritance of presenile dementia and a hypokinetic syndrome are described. In the past, these patients have carried diagnoses of Pick's disease, Huntington's disease, Parkinson-dementia, and one patient was described as suffering from a 'peculiar type of presenile dementia' in a case report. In the two cases examined, the most distinctive neuropathological features were extensive globular deposits of periodic acid-Schiff plus diastase (PAS)-positive material, having tinctural properties of amyloid only to a limited degree, in the cerebellum and cerebral cortex. These globules stained positively with antibodies against prion protein. Southern blot of MspI-digested genomic DNA showed an abnormal band of approximately 950 bp in all three patients from which material was available. Direct sequencing of the abnormal allele revealed an insert consisting of eight extra 24-nucleotide repeats in the patients, which was absent in a healthy first degree relative who was considered well beyond the age of onset of symptoms in this family. The nucleotide sequence of the abnormal insert of 192 bp was different from that of a previously described insert of equal length. Adding to previous descriptions of mutations in the prion protein gene, this report emphasizes the clinical, neuropathological and genetic heterogeneity of inherited prion disease.