PRNP P102L: research

What is the phenotype range?

Webb and colleagues (Brain 2008) assembled 84 P102L patients from a large kindred originating in central England, with emigrant branches across the English-speaking world, plus numerous small unrelated pedigrees. Many had classical Gerstmann-Straussler-Scheinker syndrome, with slowly progressive cerebellar ataxia and later cognitive impairment. A subset presented with prominent cognitive and psychiatric features, and some of those met diagnostic criteria for sporadic CJD. The series held 54 women and 30 men, which the authors attribute probably to ascertainment bias.

The Chinese national surveillance series (Wang and colleagues, Journal of Clinical Neurology 2019) found a different balance of presenting features in 12 Han Chinese patients identified from 2006 to April 2018. Movement symptoms were present in 9 of 12, rapidly progressing dementia in 7, mental symptoms in 5 and slowly progressing dementia in 2, with most patients showing more than one. Median age at onset was 50 years, range 34 to 67. Ten of the 12 recalled a disease-related family history.

Whether these two distributions reflect real population differences or differences in how cases reach a surveillance centre is not settled by either paper.

How long does the disease last?

The two series disagree, and the gap is large.

In the Chinese series, 7 patients had died at the time of writing, with median survival from onset of 16 months, range 10 to 44.

In the European multicentre cohort (Schmitz and colleagues, Brain 2022), median duration from onset to death in 14 P102L cases was 57.7 months, interquartile range 14.9 to 74.8. In the same cohort median duration was 6.0 months for E200K and 4.0 months for V210I, and the hazard ratio for P102L against E200K was 0.0806, P less than 0.001. The P102L group was 12 codon 129 MM and 2 MV, too few MV cases to test a codon 129 effect on duration.

Both cohorts are small and retrospective, and case ascertainment through surveillance networks favours rapidly progressive presentations. A reader comparing the two should treat the 16 month figure as a surveillance-ascertained subset rather than as the duration of P102L disease.

What modifies age at onset?

Webb and colleagues report two modifiers in their series. Codon 129 MM homozygosity was associated with onset about 7 years earlier than MV, P = 0.02, and the eight earliest onsets in the series were all MM. APOE4 carriers had onset delayed by about 10 years, P = 0.02. Neither modifier affected the semi-quantitative pathological score in the 10 autopsied patients. The full text of that paper sits behind a paywall and the figures here come from the abstract.

The Chinese series does not test modifiers. All 12 patients were codon 129 MM, which is consistent with the codon 129 allele distribution in East Asian populations and leaves no comparison group.

Why do standard CSF cut-offs miss P102L?

Applying the usual sporadic CJD thresholds, Schmitz and colleagues found sensitivity in the 14 P102L cases of 14 percent for 14-3-3 by western blot, 43 percent for 14-3-3 by ELISA, 43 percent for total tau, 43 percent for alpha-synuclein and 43 percent for RT-QuIC. In the same cohort V210I reached 87 to 96 percent across those markers and E200K 70 to 93 percent.

The authors derived P102L-specific cut-offs against healthy controls: 14-3-3 above 5,550 AU/ml, sensitivity 93 percent and specificity 90 percent; total tau above 659 pg/ml, 64 and 98 percent; alpha-synuclein above 311 pg/ml, 71 and 88 percent. Against neurological disease controls the same markers performed worse, 14-3-3 above 9,891 AU/ml giving 79 percent sensitivity and 79 percent specificity. The authors state that these cut-offs were derived and evaluated in the same cohort, which may bias the accuracy estimates, and that no longitudinal samples were available.

The Chinese series reports CSF 14-3-3 positive in 5 of 11 tested, MRI abnormal in all 11 scanned, and periodic sharp wave complexes on EEG in 2 of 8 tested.

Does substrate choice recover the missed cases?

Myskiw and colleagues (Annals of Neurology 2026) tested 10 archived P102L CSF samples in Canada against three seeded conversion formats. Deer mouse substrate EP-QuIC detected 10 of 10, full-length hamster EP-QuIC 8 of 10, and the truncated hamster IQ-RT-QuIC format 4 of 10. The study is retrospective, uses stored samples, and the per-variant groups are small, mostly 1 to 13 cases. The same paper reports internal inconsistencies between its abstract and its results text on overall cohort sensitivity, so per-variant counts are the more reliable figures in it.

Taken with the Brain 2022 data, the pattern across both studies is that P102L seeding activity is detectable but is poorly captured by the truncated hamster recombinant substrate that most clinical RT-QuIC services run.

Where does P102L sit among the pathogenic variants?

Appleby and colleagues (Frontiers in Neurology 2022) name P102L as one of four variants, with E200K, D178N and A117V, that together account for more than half of all genetic prion disease, and group it with D178N as nearly completely penetrant. Related pages: P105L, which is also assigned to a Gerstmann-Straussler-Scheinker phenotype, and octapeptide repeat insertions, where biomarker sensitivity falls as repeat number rises. The plain-language version is P102L explained.