Magnified 100X, and stained with H&E (hematoxylin and eosin) staining technique, this light photomicrograph of brain tissue reveals the presence of prominent spongiotic changes in the cortex, and loss of neurons in a case of variant Creutzfeldt-Jakob disease (vCJD). Variant Creutzfeldt-Jakob disease (vCJD) is a prion disease that was first described in 1996 in the United Kingdom. There is now strong scientific evidence that the agent responsible for the outbreak of prion disease in cows, bovine spongiform encephalopathy (BSE or 'mad cow' disease), is the same agent responsible for the outbreak of vCJD in humans. Both disorders are invariably fatal brain diseases with unusually long incubation periods measured in years, and are caused by an unconventional transmissible agent called a prion. vCJD is not the same disease as classic CJD. It has different clinical and pathologic characteristics from classic CJD. Each disease also has a particular genetic profile of the prion protein gene.