Alzheimer's Disease

What is Alzheimer's disease?

Alzheimer's is a disease that causes dementia, or loss of brain function. It affects the parts of the brain that are important for memory, thought, and language.

The brain of a person with Alzheimer's contains abnormal clumps of cellular debris and protein (plaques) and collapsed microtubules (support structures inside the cell). Microtubule collapse is caused by a malfunctioning protein called tau, which normally stabalizes the microtubules. In Alzheimer's patients, tau proteins instead cluster together to form disabling plaques and tangles. These plaques and tangles damage the healthy cells around them, leading to cell death. The brain also produces smaller amounts of neurotransmitters (acetylcholine, serotonin, and norepinephrine), chemicals that allow nerve cells to talk to one another.

Alzheimers Chromosome

The most common form of the disease, which strikes after age 65, is linked to the apolipoprotein E (apoE) gene on chromosome 19. Scientists don't know how apoE4 increases the risk of developing Alzheimer's. They do know that everyone has apoE, which comes in three forms.

One of the forms (apoE4) increases a person's risk of developing Alzheimer's. The other two forms seem to protect against the disease. While people who inherit the apoE4 form of the gene are at increased risk for the disease, they will not necessarily develop it.

Mutations in genes found on chromosomes 1, 14, and 21 are linked to rarer forms of the disease, which strike earlier in life.

Alzheimers Brain Plaques Tangle

How do people get Alzheimer's disease?

Scientists don't know exactly how people develop Alzheimer's, but they believe it is caused by a combination of genes and environmental factors. In other words, it is a multifactorial disorder.

The early-onset forms of Alzheimer's are inherited in an autosomal dominant pattern, which means that only one parent has to pass down a defective copy of the gene for their child to develop the disorder.

What are the symptoms of Alzheimer's disease?

Because Alzheimer's destroys brain cells, people who have the disorder slowly lose their ability to think clearly. At first, they may forget words or names, or have trouble finding things. As the disorder worsens, they may forget how to do simple tasks, such as walking to a friend's house or brushing their hair. Some people with Alzheimer's also feel nervous or sad.

Autosomal Dominant

How do doctors diagnose Alzheimer's disease?

There is no single test for Alzheimer's. Doctors use several different tests to check a patient's memory, language skills, and problem solving abilities. These tests don't diagnose Alzheimer's, but they can rule out other disorders that have similar symptoms.

How is Alzheimer's disease treated?

There is no cure for Alzheimer's, but a few medicines can slow its symptoms. A drug called Aricept increases the amount of the neurotransmitter acetylcholine in the brain. Another medicine, Namenda, protects brain cells from a chemical called glutamate, which can damage nerve cells. Doctors may also give their Alzheimer's patients antidepressants or anti-anxiety medicines to ease some of their symptoms.

People with Alzheimer's often need a caregiver—someone to help them do the things they were once able to do themselves.

Interesting facts about Alzheimer's disease

Alzheimer's was named after the German doctor, Alois Alzheimer, who first named the disorder in 1906.

The older a person gets, the higher his or her risk of getting Alzheimer's. Only about 1 or 2 people out of 100 have Alzheimer's at age 65; whereas, one out of every five people has the disorder by age 80.

As many as 4 million Americans have Alzheimer's disease.


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Genetic Science Learning Center (2014, June 22) Alzheimer's Disease. Learn.Genetics. Retrieved July 29, 2016, from
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