BMT works best when there is a 100% or 90% match of important markers on cells between the donor and the person having the BMT. A brother or sister has a 25% chance of being a perfect match and are often used as donors. A parent is usually only a 50% match so traditionally not always seen as being ideal donors, although by chance some parents may be a better match. Newer BMT techniques mean that “haplo” BMTs are being increasingly performed when no other suitable donor can be found. Haploidentical means half-identical, and these are 50% matches, usually a parent. The stem cells or bone marrow for a haplo-BMT need special treatment to remove cells that would attack the patient and the time for the immune system to get up and working again is considerably longer, but it does provide an alternative where none used to exist.