A new form of Creutzfeldt-Jakob disease (CJD has surfaced in the US. Ten have died so far died from this fast-advancing form of fatal dementia called PSPr, New Scientist reports.

Creutzfeldt-Jakob disease (CJD) is a very rare and incurable degenerative neurological disorder that is ultimately fatal. The disease was first described by German neurologists, Hans Gerhard Creutzfeldt and Alfons Maria Jakob in the first half of the last century.

It is rare and only occurs in about one out of every one million people. It usually affects people aged 45–75, most commonly appearing in people between the ages of 60–65. The exception to this is the more recently-recognised 'variant' CJD (vCJD), which occurs in younger people.

The first symptom of CJD is rapidly progressive dementia, leading to memory loss, personality changes and hallucinations. This is accompanied by physical problems such as speech impairment, jerky movements (myoclonus), balance and coordination dysfunction (ataxia), changes in gait, rigid posture, and seizures. The duration of the disease varies greatly, but sporadic (non-inherited) CJD can be fatal within months or even weeks, doctors say.

No one yet knows how the disease originates, or under what conditions it might spread. Nor is it clear how many people have the condition.

The new cases were referred to CJD surveillance units in the US because they were a suspiciously fast-advancing form of dementia with additional symptoms such as the loss of the ability to speak and move, even though traditional tests that normally help diagnose CJD proved negative.