Inherited prion disease with 5-OPRI: phenotype modification by repeat length and codon 129.
BACKGROUND
Human prion diseases have sporadic, acquired and inherited etiologies and show considerable phenotypic heterogeneity. An individual inherited prion disease offers an opportunity to study the determinants of this clinicopathologic heterogeneity among individuals with the same causal mutation.


METHODS
We report clinical and pathologic data from three families with different 5-octapeptide repeat insertion (5-OPRI) mutations of the prion protein gene (PRNP), extending the reported phenotypic range of this mutation.


RESULTS
The proband of a South African family presented with a rapidly progressive dementia and atypical pathology associated with kuru-like prion protein plaques. The original mutation in this family probably occurred on a PRNP allele encoding a 1-octapeptide repeat deletion polymorphism. This has not been previously reported as a precursor allele in over 30 other OPRI mutation kindreds. An English family with a genetically distinct mutation but identical protein product showed clinical onsets that varied 30 years between father and daughter, an effect that may be explained by their genotypes at PRNP codon 129. A patient from Northern Ireland with a phenotype of sporadic Creutzfeldt-Jakob disease presenting with visual disturbance was unexpectedly found to have a 5-OPRI.


CONCLUSIONS
When these cases were combined with the existing world literature, the mean age at onset for patients with 5-octapeptide repeat insertion (5-OPRI) was significantly later than that for patients with 6-OPRI, but both mutations exhibit a similar powerful disease modifying effect of PRNP codon 129.
Mead
S
S
MRC Prion Unit and Department of Neurodegenerative Disease, Institute of Neurology, Queen Square, London, UK.
Webb
T E F
TE
Campbell
T A
TA
Beck
J
J
Linehan
J M
JM
Rutherfoord
S
S
Joiner
S
S
Wadsworth
J D F
JD
Heckmann
J
J
Wroe
S
S
Doey
L
L
King
A
A
Collinge
J
J
D000328:Adult; D003062:Codon / Q000235:genetics; D004252:DNA Mutational Analysis; D018450:Disease Progression; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D005820:Genetic Testing; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009660:Northern Ireland; D010375:Pedigree; D010641:Phenotype; D011110:Polymorphism, Genetic / Q000235:genetics; D017096:Prion Diseases / Q000208:ethnology / Q000235:genetics* / Q000378:metabolism; D011328:Prions / Q000235:genetics*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics*; D013019:South Africa
D003062:Codon; D011328:Prions