This beautiful young woman once had her whole life ahead of her.  But today she can't control her muscles and it's a struggle just to walk down the street.

"It's a battle every day," says Desiree Jennings.

It gets even more shocking.  The 25-year-old, from suburban Washington, D.C., can't walk forward without twisting, jerky movements.  But when she walks backwards, she's perfectly normal.  She can even run with a normal stride, but once she stops, it's heartbreaking to watch.

Believe it or not, doctors at world renowned Johns Hopkins Medical Center say it's the result of a simple flu shot.

"Nothing else could explain such a fast and damaging neurological condition," Desiree says.

Americans are lining up for flu shots after dire predictions that the swine flu will sweep the country.

Desiree's life took a tragic turn just 10 days after she got a flu shot this past summer.  Doctors say it triggered a rare neurological disorder they're calling a-million-to-one reaction to the flu shot.

Dr. Marc Siegel is the author of Swine Flu, The New Pandemic.  He says Desiree suffers from dystonia.  Her twisting and jerking movements are the result of uncontrollable muscle contractions.  There's no known cure.  "It is a very very heartbreaking situation, and it certainly looks like a dystonic reaction to me.  [It's a] very, very bad neurological situation for her and my heart goes out to her," he says.

Desiree was in training to join the Washington Redskins cheerleading squad, and she had just celebrated her second wedding anniversary with her husband Brendan when her life changed.

Doctors say what happened to Desiree is extremely rare and shouldn't discourage people from getting flu shots.

"It is so rare that it is much more important to be afraid of the flu than a flu shot," says Dr. Siegel.

But stories like Desiree's are certain to raise questions.  She gets exhausted after just a few steps, loud noises can trigger seizures, and to hear her speak is to see a life in ruins.

"I want people to look at me and know this could happen," says Desiree.

The CDC says there was no problem with the vaccine Desiree received.  Dystonia is an irreversible condition.