Rapper Nicki Minaj has called on fans to join a bone marrow database after discovering her young cousin is in desperate need of a transplant.

The Super Bass hitmaker has taken to Twitter.com to urge her followers to sign up to America's National Marrow Donor Program, and she shared a link to a page with information about the donation process.

Minaj has a personal connection to the cause - her 12-year-old cousin Saidah, who is battling lupus, is waiting for a life-saving donor match.

In a post on the social networking site, Minaj writes, "Just found out my little cousin Saidah & so many more children are in need of a bone marrow transplant. We can help. Barbz, is it ok if I donate money on your behalf? I'll tell her u (you) guys send your love. She's so sweet."