Alzheimer's and Presenile dementia

Alzheimer's noun - A progressive form of presenile dementia that is similar to senile dementia except that it usually starts in the 40s or 50s; first symptoms are impaired memory which is followed by impaired thought and speech and finally complete helplessness.

Presenile dementia and Alzheimer's are semantically related. In some cases you can use "Presenile dementia" instead a noun "Alzheimer's".

Presenile dementia noun - Dementia with onset before the age of 65.

Alzheimer's and presenile dementia are semantically related. Sometimes you can replace term "Alzheimer's" with "Presenile dementia", this terms are similar.