Doctors are warning about a common form of dementia that affects thousands of people in early middle age, but is vastly overlooked or misdiagnosed as other ailments.

The dementia is call frontotemporal dementia (FTD), and it strikes earlier in life than the better-known Alzheimer's disease. But unlike Alzheimer's, which destroys a patient's memory, FTD shrinks the front lobes of the brain that control behaviour and speech.

Although most people have never heard of it, FTD is the second-most common form of dementia. It usually affects adults between the ages of 45 and 65.

Because FTD is lesser known, physicians are trying to bring more attention to the disease. They believe that if more people are able to spot the symptoms sooner, it will improve the likelihood that a patient is properly diagnosed.

Nearly 300,000 cases of FTD are diagnosed in North America each year, but doctors believe many live with the disease and its strange symptoms without a diagnosis.

The confusion stems from FTD's symptoms. At first subtle and gradual, they have been mistaken for the signs of a mid-life crisis or depression. A patient's behaviour becomes child-like but is often devoid of emotion.

Neurologist Dr. Tiffany Chow, a senior scientist at the Rotman Research Institute at Baycrest, says some people who are believed to have a substance abuse problem are actually misdiagnosed FTD patients. Others are mistakenly sent to psychiatrists to be treated for a mid-life crisis, withdrawal or stress when the problems are actually caused by FTD.

Chow said FTD should be considered when a person in the age range is going through major changes in their organization skills, personality or temper, especially if the person has no previous psychological issues.

Brian McNamara first noticed the signs of FTD in his wife Wendy when she began to spend more time alone and display some odd behaviour, although he didn't know what was causing it.

"She would go rub the sides of the trees, saying, ‘You're such a lovely tree,'" Brian McNamara told CTV News.

Adding to his concern was a change in his wife's organizational skills after 36 years of marriage. Normally a tidy person, Wendy McNamara would leave papers and dishes lying around the house.

Confused family members thought the Oakville, Ont. woman's actions were due to menopause or depression, but the symptoms persisted.

After three years, they finally learned what the problem was. McNamara said his wife's FTD diagnosis was difficult to accept because there was no way to stop it from developing even further and prevent his wife from becoming even less like her former self.

"The shocking part of it is that nothing is going to stop this, nothing's going to make it better. It will gradually get worse," he said.

Today, his wife doesn't speak, not even to family members. When she walks, she stares at the floor and follows the seam of the carpet.

"She's looking down at the pattern in the carpet and she'll walk, like a tightrope, along that line," McNamara said.

McNamara cared for his wife for three years at home but he had to put Wendy in a nursing home after her behaviour became too difficult for him to handle.

There is no known cause for FTD. Some research suggests there is a genetic link, but the vast majority of patients are random cases.

Medications are available, but the prescribed drugs don't stop the unusual accumulation of protein in the brain that is linked to the condition. After diagnosis, a person's survival is estimated to be six to 10 years.

With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip