Emily Levins was raised in San Francisco but her Ashkenazi Jewish descent has crucially shaped her identity.

The 24-year-old is one of an estimated 1 million to 2 million Americans to inherit an incurable inflammatory bowel disease, an affliction especially prevalent among Jews of Eastern European descent.

Levins suffers from ulcerative colitis, an inflammation of the large intestine. It sometimes causes her severe abdominal distress, "like knives going through my stomach," as well as a rash that covers her back, neck and chest, joint pain and extreme fatigue.

But the disease has also given her strength and determination. "It has really forced me to push myself and to be more empathetic towards others. It's part of who I am."

Although Levins believes she is the only one in her family to suffer from the disease, genetics plays a role in its development.

Dr. Jonathan Terdiman, director of the Center for Inflammatory Bowel Diseases at UCSF, said the diseases are four to five times more likely to occur in Ashkenazi Jews than in the general population.

"They have both a genetic and an environmental component," he said. "The specific genes that cause it are largely unknown, but we do know it's especially common in Jewish people."

Researchers are getting closer to finding the cause and cure.

In the May 31 issue of Nature, U.S. and French researchers published a breakthrough genetic discovery regarding Crohn's disease, which affects both the large and small intestines.

The scientists discovered an abnormal mutation in a gene known as Nod2 occurs twice as frequently in Crohn's disease patients than in the general population.

Also, a new drug, Colazel, hit the market earlier this year and should aid in the treatment of ulcerative colitis. Colazel "is not a critical advance, but it will be beneficial to those with ulcerative colitis," Terdiman said. "There's a variety of medications that can help assure people with these diseases a good quality of life. But unfortunately, because we don't know the exact causes yet, we don't have the ability to cure them."

Levins has been taking various medications for ulcerative colitis since her diagnosis at the age of 15. "I have to," she explained. Without them, "I'd be sick all the time."

Even so, shes still can get sick. As a student at University of Michigan, she suffered symptoms before final exams, but didn't let that stop her from doing well.

"It was really hard for me, but I ended up pulling it together and doing well," she said. "I did everything everyone else did: I went out with friends, I volunteered. I even joined a sorority."

After graduation, while working as a financial consultant, she never missed a day of work.

"When I was younger I was embarrassed by this, but I'm not embarrassed anymore," said Levins, who is writing a book for teens about coping with chronic illnesses.

Terdiman urges anyone with symptoms of an inflammatory bowel disease to get a doctor's exam. Symptoms include diarrhea, blood in the stool, abdominal pain and cramping, poor appetite, fever and fatigue.