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Protease-resistent PrP was found in both patients with fatal familial insomnia,but the size and number of protease-resistent fragments differed from those in Creutzfeldt-Jakob disease.In the family with fatal familial insomnia,all 4 affected members and 11 of the 29 unaffected members had a point mutation in PrP codon 178 that results in the substitution of asparagine for aspartic acid and elimination of the Tth111 I restriction site.Linkage analysis showed a close relation between the point mutation and the disease(maximal lod score,3.4 when 0 was zero).Fatal familial insomnia is a prion disease with a mutation in codon 178 of the PrP gene, but the disease phenotype seems to differ from that of previously described kindreds with the same point mutation. |
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