Until relatively recently, bone marrow grafts from sibling donors were the only stem cell source available to patients in need of a transplant. The establishment of haematopoietic stem cell donor registries and public cord blood banks worldwide has increased the availability of grafts from unrelated donors for patients requiring stem cell transplantation.
The safety of the volunteer donor is an extremely important issue for the Donor Centres and a series of laboratory tests along with medical assessment are now mandatory. Donors are considered eligible for the donation when all medical data conclude that they are healthy. This assessment has a dual purpose. That is, not only to avoid placing the life of the donor at risk by aggravating asymptomatic health problems, but also to protect the recipient from the transmission of viruses and any other potentially transmissible disease. Although volunteer donors are not screened for genetic diseases, it is assumed that donors with genetic diseases are deferred as this can be deduced from the medical history or from findings of the laboratory tests undertaken.
Transmission of genetic diseases by cord blood units has a significantly higher risk than stem cells from peripheral or bone marrow donation since the disease might not be easily recognised at birth or even for some time later. Although public cord blood banks request that information on the health status of the newborn/donor be provided by the family even sometime after the donation and prior to the listing of the unit, it is possible that some genetic diseases will be missed as they might not manifest until much later in life.
Theoretically, all congenital diseases originating from bone marrow-derived cells are transmissible. Very few cases of genetic disease transmission through haematopoietic cells have been reported. Cyclic neutropenia and Gaucher’ s disease were transmitted via sibling HPC transplantation (81). In addition, a variety of autoimmune diseases have been transmitted including: Hyperthyroidism and autoimmune thyroiditis and thyrotoxicosis, alopecia areata, type 1 diabetes, atopy, autoimmune thrombocytopaenia, myasthenia gravis, vitiligo, asthma and anti-Ciq antibodies of systemic lupus erythematosus (SLE).
According to the EU Directives for tissues and cells, genetic disease transmission by tissues and cells is considered an adverse reaction and, as such, should be reported to the Competent Authority and investigated to confirm the transmission.
Recommendations:
1. Donors originating from areas with a high frequency of certain genetic diseases should, if the risk is identified during the medical examination, be screened for the disease, and if found to be positive, should be deferred.
2. The medical history questionnaire for cord blood donation should cover maternal and family history and the expectant parents’ ethnic background. If responses generate medical concern then the application/collection should be rejected/cancelled.
3. Cord blood units that are or were collected from families that are potential carriers of genetic diseases should be screened prior to listing and use and if found positive to be discarded. Mechanisms to inform the family should be in place.
4. Cord blood banks that have stored cord blood units that are not found to carry a genetic disease but show the trait of a genetic disease e.g. trait of beta thalassaemia, should provide this information to the transplant centre requesting the release of the unit.
5. The cord blood from babies that were conceived through the use of donor gametes should not be collected and stored unless the medical history of the sperm donor is available. If an oocyte donor is involved, blood samples from the oocyte donor can be collected.