Alzheimer's disease

Alzheimer's disease is a terminal, progressive disease of the brain. Although it's not fatal in-and-of itself, its progression results in a patient eventually being unable to cope with routine daily tasks and, ultimately, being totally unable to care for themselves.
Alzheimer's usually presents as an inability to do tasks the patient typically did on a routine basis. Patients may be unable to perform the tasks required of their work. Next, short term memory starts to disappear, with patients being totally unable to remember what task they are supposed to be performing. Finally, the patient is unable to remember anything that happened even a few minutes previously, and becomes increasingly unable to do routine chores, such as dressing themselves.
Unlike other patients who are suffering from loss of short-term memory or cognitive difficulties, Alzheimer patients often refuse to cooperate with tests of these abilities. For example, when faced, with a common test of counting backwards from 100 by 7, people with most cognitive difficulties will fail to pass the test and realize they are failing, those with other short-term memory difficulties will gladly fail the test over and over again, but Alzheimer's patients will take active steps to avoid taking the test, such as calling into question the need for the test or say they have something else they have to do.
There is no cure or treatment for Alzheimer's and, once diagnosed, the prognosis is that the disease will get worse. Alzheimer's patients often have to be kept under close supervision to keep them from hurting themselves, such as by trying to cook a meal. In the later stages, palliative care is all that is possible as patients are often unable even to communicate.