Ms. Tavarez underwent a transplant of umbilical cord blood on Aug. 17 in an effort to battle acute myelogenous leukemia. She inspired thousands to offer themselves as potential bone-marrow matches in several marrow drives earlier this year. A bone marrow match could not be found, so the umbilical cord procedure was attempted.

Ms. Tavarez died Monday afternoon at Cohen Children's Medical Center in New Hyde Park, on Long Island, according to Katharina Harf, co-founder of the bone marrow donor center DKMS.

Due to her illness, the young actress left the Broadway show in April. She shared the part of Young Nala with another actress for six months.

The Queens, New York, native was in the sixth grade, and, according postings on her website earlier this year, loved doing what most young kids with stars in their eyes loved doing — "acting, singing, dancing, playing Wii and watching 'Glee.'"

Ms. Tavarez, who is of mixed-race heritage, had a particularly difficult time finding a match because there are fewer registered marrow donors from such demographics. Touched by her effort to find a donor, pop stars Alicia Keys, Rihanna and 50 Cent picked up the banner and helped encourage people to contribute to the life-giving process. Her mother is African-American and her father is Dominican. African-Americans make up only seven percent of the national registry for donors, according to DKMS, the largest bone marrow donor center in the world. "Shannon inspired 10,000 donors to register to become potentially life-saving matches with DKMS and we've already found potential matches," Harf told Playbill.com. "Shannon's family is devoted to continuing her mission to recruit donors."

Potential donors get a simple saliva swab and results are put into a wide database that may lead to helping others stricken with cancer. For information about how to register to be a bone marrow donor, visit www.getswabbed.org.