SUFFERERS of severe combined immunodeficiency (SCID) are prone to infections and diseases.  Their bone marrow stem cells are defective and cannot produce white blood cells to fight infections.  David Vetter, a SCID sufferer, lived his entire life inside a sealed plastic bubble. He died when he was 12.  In 1976, his story was made into a movie, The Boy In The Plastic Bubble, which starred John Travolta.  The disease then came to be known as 'Bubble Boy' disease.  The disease is so rare that between 1990 and 2000, doctors here have diagnosed only two cases.  Both were infants and died within a year, a report in the Singapore Medical Journal (2003) stated.  SCID sufferers' only hope would be a stem-cell transplant from cord blood...