| Abstract: | Surveillance of Creutzfeldt-Jakob disease (CJD) was reinstituted in the United Kingdom in 1990 to monitor any effects of the bovine spongiform encephalopathy (BSE) agent on humans. In 1996, the CJD Surveillance Unit described a new variant of CJD, characterised by an unusually early age of onset, a prolonged clinical course with presenting features that were unusual for CJD, and a characteristic neuropathology. All patients were homozygous for methionine at codon 129 in the prion protein gene, with no mutations or insertions. At present, 23 patients have been diagnosed with this new disorder, but it is impossible at present to predict likely numbers of future cases. Strain typing studies in experimental mice have shown that the transmissible agent in new-variant CJD has identical features to that of the BSE agent, but differs from that in sporadic CJD. The identification of disease-associated prion protein in lymphoid tissue in newvariant CJD raises the possibility of lymphoid biopsy for early diagnosis, and indicates that the transmissible agent may be present in association with circulating lymphoid cells in the blood and other tissues. Although the mode of transmission of the BSE agent to humans is unknown, current evidence favours a dietary mode of spread. However, the precise route of spread, infectious dose and incubation period for BSE in humans are all unknown. Additional studies are required to provide further information, which will allow a more accurate understanding of disease pathogenesis and prediction of future disease trends. |
