CJD case had different gene

British scientists have warned more people may be incubating variant CJD after finding that the latest victim had a different genetic make-up from the other cases diagnosed around the world. The 30-year-old man was admitted to hospital in 2008 with a 13-month history of personality change, progressive unsteadiness and intellectual decline. He later developed visual hallucinations and was diagnosed with vCJD before his symptoms worsened and he died two months later. Scientists noted in The Lancet  the case is unusual because the man had a prion protein gene (PRNP) that was heterozygous; however, in every case studied to date, subjects have been methionine (MM) homozygous. They noted that other prion diseases tend to have longer incubation periods in those who are heterozygous than those who are MM homozygous. “Therefore, we believe there could be similar cases in which people are infected with vCJD but experiencing a long incubation period,” they said. They said the majority of the UK population have potentially been exposed to the infection but added that the extent of clinically silent infection is still ‘unclear’. About a third of the UK population are PRNP MM homozygous… [and so] further cases, which may or may not meet diagnostic criteria for vCJD, would be expected in these [people].” “However, prion disease susceptibility and incubation periods are also affected by other genetic loci, and the possibility remains that cases of vCJD to date may have unusual combinations of genotypes at these loci, yet to be fully characterised,” they concluded. Lancet 2009; 374: 2128...