By Emily Riemer, Anchor/Medical Reporter

Huntington's disease is a genetic condition doctors describe as a combination of Lou Gehrig's, Parkinson's and Alzheimer's diseases. It is always fatal, but a new treatment being tested in Boston that could change that devastating outcome.

Michelle Herlihy was just a young woman when her father was diagnosed with Huntington's disease.

"It was a complete shock to our family." Herlihy said.

Her grandmother died at 77 from what the family thought was Parkinson's disease. When her father started experiencing movement symptoms, Herlihy thought he might have it, too.

"They (the doctors) thought it might be Parkinson's. They were going to rule it out. We were all hoping for that, but they ruled it in," Herlihy said.

Huntington's disease is a fatal genetic disease. It affects movement, mood and memory. It's considered rare, with 30,000 people in the United States reporting symptoms. Currently, there is no treatment to slow it down.

After her father's diagnosis, Herlihy made a choice not to have genetic testing to see if she, too, had the disease.

"I knew there was no cure. There was absolutely no treatment. I just decided that it's better to live my life a little, try to enjoy," Herlihy said.

Dr. Samuel Frank is in the department of neurology at Beth Israel Deaconess Medical Center.

Frank said researchers know what causes Huntington's disease: extra copies of a specific gene on the fourth chromosome that cause abnormal protein.

"If we can reduce the abnormal protein that's causing problems, hopefully we can do something to the underlying disease itself," Frank said.

Now, researchers may be able to do just that. Frank is leading a clinical trial testing a new therapy developed by Genentech/Roche called RG6042. Early results are promising.

Findings published in the New England Journal of Medicine showed the medicine significantly reduced abnormal huntingtin protein.

"It's huge. We're not just talking statistically significant. It's a meaningful reduction from a biomarker perspective," Frank said.

Now, researchers will study whether it reduces symptoms as well.

It's promising news for people like Michelle Herlihy. In January, she decided she wanted to know her disease status, was tested and learned she does have Huntington's disease.

She manages symptoms with exercise for now and said this potential therapy is the hope so many have waited for.

"It's like we're looking for the pot at the end of the rainbow and that's a cure," Herlihy said.

The RG6042 clinical trial is enrolling for the Boston site right now. Six hundred sixty people at sites around the world will be included.

Frank has worked in this field since 2002 and said this the most optimistic time he's witnessed in the Huntington's disease community.

The Huntington's Disease Society of America offers information about the disease as well as resources for patients.