It usually presents in late middle-age with progressive dementia, and is usually fatal within 6 months. It is characterised by spongiform changes in the brain, but this can only readily be diagnosed at post mortem. CJD occurs worldwide at an annual incidence rate of 0.5-1 per million per annum. To date, the UK annual incidence remains within expected limits - in 1994 the incidence was 0.92 per million and the provisional figure for 1995 is 0.64 per million. In the last two weeks, the CJD Surveillance Unit have described a distinct variant of CJD -in 10 cases, in people aged under 42 with dates of onset of illness in the last two years.
Brain pathology shows marked spongiform change and extensive florid plaques throughout the brain.
As with typical sporadic CJD, symptoms in the early stages may be fairly non-specific. These 10 cases have been carefully reviewed with respect to their clinical and pathological features, and do not appear to be explained by increased ascertainment. An iatrogenic factor has not been identified, and in the absence of any other more credible alternative, a possible explanation at present is that these cases are linked to exposure from cattle infected with BSE before the SBO ban in 1989. It is not possible to predict how many further cases there will be. Even with the new variant the incidence last year was less than one in a million.