The age of onset and penetrance is impossible to predict accurately for individual cases. When conditions with incomplete penetrance, and varying age of onset and expressivity are considered for licensing, GIG believes that the condition should be licensed by considering the worst possible case that can be reasonably expected.
The 'treatability' of these conditions should not be considered as an argument against the use of PGD to prevent affected births, except where such a treatment will be minimally invasive, and allow the affected child to expect a normal life free from restriction. None of the late-onset conditions currently licensed for PGD have such treatments available.
My final point on late-onset conditions is the issue of time. The time delay imposed by using a case-by-case licensing process instead of a condition-by-condition licensing process is especially harmful for patients with some late-onset conditions. To return to the example of inherited cancer, one of the prophylactic treatment options available is preventative oophorectomy. This measure of course must be taken after the PGD process has been completed, and increases the need for the process to be as quick as possible. A case-by-case approach to licensing lengthens an already lengthy and difficult process.
Dr King presents no advantage to case-by-case licensing of PGD for tissue typing to conceive a saviour sibling as opposed to condition-by-condition licensing. I present a disadvantage: the time factor. The time delay imposed by using a case-by-case licensing process instead of a condition-by-condition licensing process is especially harmful for families with a sick child who could benefit from a sibling donation of cells or tissue. The affected sibling may have a very short life expectancy and, as I have already stated, the case-by-case approach to licensing lengthens the process. To maximise chances of success of such a donation delays should be minimised.
In his arguments against the use of tissue typing to conceive a saviour sibling, Dr King calls for this to be a last resort. All of those who have met a family who have or are trying to conceive a saviour sibling can assure Dr King that this is indeed the case.
GIG sees no constructive benefit gained by maintaining case-by-case licensing for either PGD for late-onset conditions or PGD involving tissue typing.