Cancer-Stricken Teen's Plea for Rare Bone Marrow Donor Goes Viral

— -- A 13-year-old teen's call for help finding a bone marrow donor has gone viral.

Zara Al Shaikh, of Hampshire, United Kingdom, was diagnosed with leukemia at age 11. She went into remission the following year, but this month her doctors found the cancer had returned. To save her this time, doctors need to find a bone marrow donor, said her father, Dr. Loua Al Shaikh, an intensive care physician and anesthesiologist.

Al Shaikh said his daughters' doctors explained that her ethnicity -- her mom is white and her dad is of Middle Eastern heritage -- may make it more difficult to find a donor, which has to match tissue type. Zara is now in a hospital in Hampshire, where she's undergoing chemotherapy.

"It’s just a few days ago when Zara and I were sitting in hospital and we looked at these social media things online," Al Shaikh told ABC News, noting he and Zara though that they could "post something out there and someone might grab it."

Zara started a Twitter account with one of her first tweets asking for people to register as a stem cell or bone marrow donor.

"It just went mad," Al Shaikh said Tuesday of the post spreading over social media. "It’s gone just absolutely viral."

The post has been retweeted more than 12,000 times and the hashtag #Match4Zara has gone viral, with many people writing in to ask how they can take join the registry. Al Shaikh said officials at one bone marrow registry told him they had a "twelve fold" increase in the number of people who signed up in a single day, after the tweet went viral.

While Zara is still without a match, Al Shaikh said he's hopeful because so many people have reached out to join the registry to see if they can help her.

"People are answering the call, so social media is doing its thing," he told ABC News. "These are regular folk and it makes you believe in humanity."

Zara is currently undergoing chemotherapy so that doctors can perform a bone marrow transplant once they find a donor.

Despite the illness, Al Shaikh said his daughter is like any other teenager and even used her cancer treatment as an excuse to dye her hair blue.

"Zara, she’s very popular but shy," Al Shaikh said. "She loves what a 13-year-old loves. She shocked us when she wanted to dye her hair blue. She said, 'But Daddy, I’m only going to lose it and I love it.'"