Lives to save lives--the ethics of tissue typing.

Should we allow tissue typing of in vitro embryos in order to implant those which could provide potentially life-saving cells to an existing serious ill sibling with that tissue type? A case is made that such tissue matching does not involve unacceptable instrumentality towards or commodification of children. The key distinction is that the parents' request for tissue typing is reactive in the face of serious medical need rather than being proactive in the sense of seeking the means to specify a child with chosen desirable characteristics. Nevertheless, as preimplantation genetic diagnosis (PGD) is a relatively new technique, both long-term safety issues concerning effects on child development following embryo biopsy and the risks of misdiagnosis must be given due weight as must the avoidance of exploitation of couples desperate to save a sick child. The HFEA originally made a distinction, recently revoked, between allowing tissue typing after PGD to select against affected embryos and denying it when PGD is not required because the embryos are not at risk of inheriting the disease suffered by the existing sibling. If tissue typing is not inherently unethical and misdiagnosis poses a greater risk than biopsy damage, then this distinction is not ethically tenable.