FRIDAY, Feb. 11 (HealthDay News) -- A year before Jim Munroe was diagnosed with a rare and aggressive form of leukemia, a 19-year-old girl from Milwaukee had her cheek swabbed at a summer rock concert.

She ended up saving Munroe's life by becoming his bone marrow donor.

Munroe, 31, of Colleyville, Texas, said he started feeling sick in late November 2008. His head hurt a lot, and he began to feel very lethargic.

"I developed a really unbearable pain in my leg that they initially diagnosed as a blood clot," Munroe said. The pain kept increasing, even after Munroe started taking a blood-thinning medication, so doctors performed more tests and determined that he had leukemia.

"The bone in my leg was swelling because of the amount of white blood cells being produced in my marrow," he said. "The doctor said if it went on, the bone would break on its own."

Doctors at the M.D. Anderson Cancer Center in Dallas recommended aggressive treatment. Munroe said he was told that he could die in three or four months if nothing was done and that, with his type of leukemia, chances of a relapse were 99 percent, even if he went into remission.

What he needed was a bone marrow transplant. "I needed to have my immune system completely replaced," Munroe said. "I needed to have it re-booted, essentially, and I needed to have someone else's healthy white blood cells to replace my own."

Munroe's doctors sent his DNA to the national bone marrow registry, hoping to find a suitable donor. They located 16 possible genetic matches for him, from 7 million people in the registry, and asked the potential donors to come in for further testing.

"With this particular transplant, they needed to find someone in the world whose DNA matched mine so perfectly that my body would recognize their immune cells as being O.K.," he said.

One of the donors matched perfectly. "They found out she was what doctors call a 10 out of 10 match, which is about the best you can hope for," Munroe said.

The young woman had signed up for the registry at a Warped tour concert, inspired by one of her favorite musicians who had gotten a marrow donation from his sister, Munroe later learned.

She took medication to boost her marrow's production of stem cells, and five days later had blood drawn and the excess stem cells filtered off. After she had the blood drawn, she had a tattoo done at the needle's entry point to signify the piece of herself she'd given away, Munroe said.

In the meantime, doctors had gotten Munroe's leukemia into remission through chemotherapy. They then destroyed his immune system with chemotherapy to prepare him for the transplant. Munroe had to be kept in isolation for a month during the process, to protect him from infection.

"On the tenth day, they brought her blood into my hospital room and began to drip it into my IV," he said. "They sit there really patiently for the first hour. The first hour is a good sign of whether the body will accept or reject what's being put into it. Their hope is the new healthy white blood cells will eat up the old nasty system you had."

The transplant took, although Munroe said that his body is still recuperating from the experience.

A year after the transplant, Munroe learned the identity of his donor. He reached out to her through Facebook to thank her. They've been corresponding ever since, and he said he hopes to meet her soon.

"I sent her an e-mail and said, 'Look, you saved my life,'" Munroe said. "'You saved my wife from being a widow. You saved my children from being fatherless. You are a hero of ours.'"

More information

A companion article on donating blood and organs offers more on what's involved.