7-month-old Billy might be the world’s smallest Tom Petty fan. And Christina, a music therapist at Children's Hospital of Wisconsin, wrote a special song just for him. A few days after he was born, Billy was diagnosed with severe combined immunodeficiency (SCID). He essentially had no immune system. About seven weeks ago, Billy received a bone marrow transplant from his big sister Cece and he’s been recovering nicely in our MACC Fund Center for Cancer and Blood Disorders ever since. Not only do his weekly music therapy sessions help raise his spirits, but they also improve his sensory stimulation and motor skills.