Savior sibling
Encyclopedia
A savior sibling is a child who is born to provide an organ or cell transplant to a sibling that is affected with a fatal disease, such as cancer
or Fanconi anemia
, that can best be treated by hematopoietic stem cell transplantation.
The savior sibling is conceived through in vitro fertilization. Fertilized zygotes are tested for genetic compatibility (human leucocyte antigen (HLA) typing), using preimplantation genetic diagnosis
(PGD), and only zygotes that are compatible with the existing child are implanted. Zygotes are also tested to make sure they are free of the original genetic disease. The procedure is controversial.
, Diamond-Blackfan anemia
and β-thalassemia, in the ailing sibling, since the savior sibling can be selected to not have inherited the disease. The procedure may also be used in children with leukemia
, and in such cases HLA match is the only requirement, and not exclusion of any other obvious genetic disorder.
Multiple embryos are created and preimplantation genetic diagnosis
is used to detect and select ones that free of a genetic disorder
and that are also a HLA match for an existing sibling who requires a transplant. Upon birth, umbilical cord blood
is taken and used for hematopoietic stem cell transplantation.
The main ethical argument against is the possible exploitation of the child, e.g. potential adverse psychological effects on a child born not for itself but to save another.
A survey of 4,000 Americans showed that most of them approved of PGD use for savior siblings.
and collaborators described the first case in 2001.
, later adapted into a film
is about a child who was born as a savior sibling.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
or Fanconi anemia
Fanconi anemia
Fanconi anemia is a genetic disease with an incidence of 1 per 350,000 births, with a higher frequency in Ashkenazi Jews and Afrikaners in South Africa.FA is the result of a genetic defect in a cluster of proteins responsible for DNA repair...
, that can best be treated by hematopoietic stem cell transplantation.
The savior sibling is conceived through in vitro fertilization. Fertilized zygotes are tested for genetic compatibility (human leucocyte antigen (HLA) typing), using preimplantation genetic diagnosis
Preimplantation genetic diagnosis
In medicine and genetics pre-implantation genetic diagnosis refers to procedures that are performed on embryos prior to implantation, sometimes even on oocytes prior to fertilization. PGD is considered another way to prenatal diagnosis...
(PGD), and only zygotes that are compatible with the existing child are implanted. Zygotes are also tested to make sure they are free of the original genetic disease. The procedure is controversial.
Indications
A savior sibling may be the solution for any disease requiring hematopoietic stem cell transplantation (see Conditions treated with bone marrow transplantation). It is effective against genetically detectable (mostly monogenic) diseases, e.g. Fanconi anemiaFanconi anemia
Fanconi anemia is a genetic disease with an incidence of 1 per 350,000 births, with a higher frequency in Ashkenazi Jews and Afrikaners in South Africa.FA is the result of a genetic defect in a cluster of proteins responsible for DNA repair...
, Diamond-Blackfan anemia
Diamond-Blackfan anemia
Diamond–Blackfan anemia , also known as Blackfan–Diamond anemia and Inherited erythroblastopenia, is a congenital erythroid aplasia that usually presents in infancy. DBA patients have low red blood cell counts . The rest of their blood cells are normal...
and β-thalassemia, in the ailing sibling, since the savior sibling can be selected to not have inherited the disease. The procedure may also be used in children with leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
, and in such cases HLA match is the only requirement, and not exclusion of any other obvious genetic disorder.
Procedure
Preimplantation genetic diagnosis
In medicine and genetics pre-implantation genetic diagnosis refers to procedures that are performed on embryos prior to implantation, sometimes even on oocytes prior to fertilization. PGD is considered another way to prenatal diagnosis...
is used to detect and select ones that free of a genetic disorder
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....
and that are also a HLA match for an existing sibling who requires a transplant. Upon birth, umbilical cord blood
Cord blood
Umbilical cord blood is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells which can be used to treat hematopoietic and genetic disorders.-Collection:...
is taken and used for hematopoietic stem cell transplantation.
Laws
- In the United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, the Human Fertilisation and Embryology AuthorityHuman Fertilisation and Embryology AuthorityThe Human Fertilisation and Embryology Authority is a statutory body in the United Kingdom that regulates and inspects all UK clinics providing in vitro fertilisation, artificial insemination and the storage of human eggs, sperm or embryos. It also regulates Human Embryo research...
(HFEA) has ruled that it is lawful to use modern reproductive techniques to create a savior sibling. - In Victoria, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, use of PGD for HLA typing is reviewed by the Infertility Treatment Authority on a case-by-case basis.
Ethical considerations
Arguments for or against the use of PGD/HLA tissue typing are based on several key issues including the commodification and welfare of the donor child.The main ethical argument against is the possible exploitation of the child, e.g. potential adverse psychological effects on a child born not for itself but to save another.
A survey of 4,000 Americans showed that most of them approved of PGD use for savior siblings.
History
Yury VerlinskyYury Verlinsky
Yury Verlinsky was a Russian-American medical researcher specializing in embryo and cellular genetics He is best known as a pioneer in prenatal diagnosis for detecting genetic and chromosomal disorders six weeks earlier than standard amniocentesis...
and collaborators described the first case in 2001.
Popular Culture
The novel My Sister's KeeperMy Sister's Keeper
My Sister's Keeper is a 2004 novel written by New York Times Best Selling author Jodi Picoult. It tells the story of 13-year-old Anna, who litigates her parents for medical emancipation when she is expected to donate a kidney to her sister Kate, who is dying from leukemia.-Plot:The story takes...
, later adapted into a film
My Sister's Keeper (film)
My Sister's Keeper is a 2009 American drama film directed by Nick Cassavetes and starring Cameron Diaz, Abigail Breslin, Sofia Vassilieva, and Alec Baldwin...
is about a child who was born as a savior sibling.