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Predictive testing for inherited prion disease: report of 22 years experience.

ABSTRACT: The inherited prion diseases (IPD) are a group of untreatable neurodegenerative diseases that segregate as autosomal dominant traits. Mutations in the prion protein gene (PRNP) were first found to be causal of IPD in 1989, before the molecular genetic characterisation of any other neurodegenerative disease. Predictive testing for IPD has subsequently been carried out at a single UK clinical and research centre for 22 years. We have analysed the uptake, consequences and factors influencing the decision for predictive testing over this period. In all, 104 predictive tests were done on individuals at 50% risk, compared with 135 positive diagnostic tests. Using genealogies from clinical records, we estimated that 23% of those at 50% risk have completed testing. There was no gender bias, and unsurprisingly, there was a slight excess of normal results because some patients were already partly through the risk period because of their age. An unexpectedly large number of patients developed symptoms shortly after predictive testing, suggesting that undisclosed early symptoms of disease may prompt some patients to come forward for predictive testing. Fifteen per cent of predictive tests were done >10 years after molecular diagnosis in a proband. A strong determinant of the timing of testing in these patients was a second diagnosis in the family. IPD may generate infectious prions that might be transmitted by surgical procedures; however, we found no evidence that public health information influenced decisions about predictive testing.

SUBMITTER: Owen J

PROVIDER: S-EPMC4091984 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The largest kindred with inherited prion disease P102L, historically Gerstmann-Sträussler-Scheinker syndrome, originates from central England, with émigrés now resident in various parts of the English-speaking world. We have collected data from 84 patients in the large UK kindred and numerous small unrelated pedigrees to investigate phenotypic heterogeneity and modifying factors. This collection represents by far the largest series of P102L patients so far reported. Microsatellite and genealogical analyses of eight separate European kindreds support multiple distinct mutational events at a cytosine-phosphate diester-guanidine dinucleotide mutation hot spot. All of the smaller P102L kindreds were linked to polymorphic human prion protein gene codon 129M and were not connected by genealogy or microsatellite haplotype background to the large kindred or each other. While many present with classical Gerstmann-Sträussler-Scheinker syndrome, a slowly progressive cerebellar ataxia with later onset cognitive impairment, there is remarkable heterogeneity. A subset of patients present with prominent cognitive and psychiatric features and some have met diagnostic criteria for sporadic Creutzfeldt-Jakob disease. We show that polymorphic human prion protein gene codon 129 modifies age at onset: the earliest eight clinical onsets were all MM homozygotes and overall age at onset was 7 years earlier for MM compared with MV heterozygotes (P = 0.02). Unexpectedly, apolipoprotein E4 carriers have a delayed age of onset by 10 years (P = 0.02). We found a preponderance of female patients compared with males (54 females versus 30 males, P = 0.01), which probably relates to ascertainment bias. However, these modifiers had no impact on a semi-quantitative pathological phenotype in 10 autopsied patients. These data allow an appreciation of the range of clinical phenotype, modern imaging and molecular investigation and should inform genetic counselling of at-risk individuals, with the identification of two genetic modifiers.

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Predictive testing for inherited prion disease: report of 22 years experience.

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