Wendy Williams has frontotemporal dementia. What is FTD?

Wendy Williams has been diagnosed with a form of dementia, according to a statement released Thursday on behalf of her caretakers.

The 59-year-old former talk show host was diagnosed last year with with primary progressive aphasia and frontotemporal dementia "after undergoing a battery of medical tests," according to the statement.

A look at the condition, which also affects the actor Bruce Willis.

WHAT IS FRONTOTEMPORAL DEMENTIA?

Frontotemporal dementia, or FTD, is a rare disease that affects parts of the brain controlling behavior and language. These parts of the brain shrink as the disease gets worse.

FTD usually occurs in people in their 40s, 50s and early 60s. It can affect a person's personality, causing a loss of inhibition or inappropriate behavior. It is sometimes mistaken for depression or bipolar disorder, and can take years to diagnose.

"It's a really tough diagnosis, I have to tell you," said Johns Hopkins University cognitive scientist Brenda Rapp. "Maybe you're doing things that are bothering people and you don't really understand why they're bothering people." That can be frustrating for everyone involved, Rapp said.

The disease often includes primary progressive aphasia, which means it's causing problems with language skills. A person with this type of FTD may have trouble finding words or understanding speech.

WHAT CAUSES FTD?

It's caused by damage to neurons, the brain's information carriers, but the underlying reasons for a particular case are often unclear. People with a family history of the condition are more likely to develop it. But most people with FTD have no family history of dementia.

CAN FTD BE TREATED?

There is no cure for FTD, but there are strategies for dealing with it. People might get speech therapy if they have the type that affects language. They might get physical therapy to improve movement.

Some patients receive antidepressants or drugs for Parkinson's, which has some overlapping symptoms with FTD.

HOW FAST DOES FTD PROGRESS?

FTD can be a long illness, lasting two to 10 years. People with FTD will need caregiving or nursing support as their symptoms get worse.

"The disease will spread throughout the brain," Rapp said. "The rate at which it does that is extremely unpredictable. So it's very hard to know … how quickly someone will deteriorate."

The financial burden on families can be immense. The Alzheimer's Association estimates it costs $10,000 a year, on average, for the out-of-pocket health and long-term care for a person with dementia.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Science and Educational Media Group. The AP is solely responsible for all content.