A new form of brain disease, similar to Creutzfeld-Jakob Disease, could affect more people than previously thought, researchers in the US say.
It had been thought that only people with one genetic profile were vulnerable to the prion disease VPSPr.
But in an Annals of Neurology study, Case Western Reserve University experts found people with all three possible gene patterns are affected by VPSPr.
They say the findings could help with the treatment of prion diseases.
Although it is a prion disease like vCJD, VPSPr is not linked to eating infected meat.
However, like CJD, the new condition happens sporadically.
It was first identified because of the fast-advancing form of dementia seen in those affected. They were also unable to speak or move.
But tests for CJD proved negative.
Further molecular examination showed VPSPr was a prion disease, but one which looked very different to those already known.
The human prion protein gene comes in three variants, depending on which amino acid the prion proteins contain - valine (V) or methionine (M).
People can be VV, MM or MV.
The first clutch of cases identified all had the VV variant. However, these latest cases included people with the other variants too.
Despite extensive research, a relatively large group of neurodegenerative diseases associated with dementia remain undefined.
Pierluigi Gambetti, a professor of pathology at Case Western who led the research, told the BBC: "Since this new disease shows several differences to other prion diseases, it is most likely that VPSPr is caused by a mechanism that is different from other prion diseases currently known.
"This newly identified human prion disease provides us with an excellent opportunity to investigate new ways of causing the disease that abnormal prion proteins may follow.
"This in turn may facilitate our efforts to develop therapeutic strategies for these devastating neurodegenerative disorders."