Study on the brains of twins finds that Alzheimer's disease is actually a diverse collection of diseases, symptoms and pathological changes. In a unique study, an international team of researchers compared the brains of twins where one or both died of Alzheimer's disease. They found that many of the twin pairs not only had similar progressions of Alzheimer's disease and dementia prior to death, but they also had similar combinations of pathologies -- two-or-more unconnected areas of damage to the brain. The researchers had the rare opportunity to directly autopsy the brains of seven pairs of twins who both died after being receiving diagnostic evaluations over many years, including a pair of identical twins who were both diagnosed with Alzheimer's and died within a year of one another at the age of 98.