The pre-implantation genetic diagnosis program (PGD) consists of the genetic study of the embryos before being transferred to the uterus, with the aim of discarding those showing genetic abnormalities. With the PGD, a lot of numeric and chromosome structural abnormalities (Aneuploidy) can be ruled out - such as genetic mutations that can lead to monogenetic diseases that may be transmitted via the dominant-recessive way, or according to the gender of the future embryo.
At CREA, where quality excellence is a priority, we count on the collaboration of Sistemas Genomicos.S.L, who are pioneers in the latest advances in reproductive medicine and genetics and whose best professionals in these fields work closely with the CREA team.
When to perform a study of Aneuploidy?
On women with advanced reproductive age; It has been shown that as time passes - mainly from the age of 37, the chance of having embryos with chromosome alterations increases, leading to a large number of miscarriages and foetuses with complications.
The other indication is for women with recurrent pregnancy loss, regardless of the age of the patient, when the percentage of abnormal embryos is higher than 70 percent.
In cases of a severe masculine factor when there is a high percentage of sperm that are carriers of genetic alterations. In these cases, a study will be previously performed through FISH (fluorescence in situ hybridisation) to discover which sperm chromosomes are affected.
In those cases where couples that have undergone previous cycles of assisted reproduction in which no pregnancy was achieved and where apparently normal embryos were transferred. In these cases, we find a high percentage of anomalous embryos, possibly explaining the previous failures.
How to deal with a monogenic disease?
Monogenic diseases are due to the presence of mutations in the genome, and depending on the mode of inheritance (dominant or recessive) will affect the future descendant of the couple in different ways.
This is why these mutations have to be carefully diagnosed, since the localization of the mutation can vary within the illness itself.
Firstly, the couple should receive genetic advice from a specialist, who will explain the consequences the disease may have on the future gestation and also offer help in taking the most appropriate decision.
After performing a karyotype on both partners, and once the mutation is located, a study called a "report study" will be carried out in order to prepare the technique for diagnosing the embryo. Once the report study has been completed, the treatment cycle can begin where the embryo DGP will be carried out.
In cases of punctual mutation, meaning when it affects only one base of the DNA chain, the technique of mini-sequences can be used enabling us to locate this minimal mutation. The application of this technique, in only one cell, from an embryo that has reached the eight-cell phase, enabled us to achieve the first Cystic Fibrosis free birth of a child in Spain, diagnosed by mini-sequences and where each of its parents was a carrier of a different mutation. Also, through mini-sequences we achieved the pregnancy in a woman carrier of Osteogenesis Imperfecta, and at that time, there had been no description of this technique worldwide.
In cases when the mutation is not punctual but affects one sequence of the DNA bases, the diagnosis is made through another molecular technology known as analysis of fragments or the use of haplotype. All in all, the combined use of these procedures allows us to analyse the embryos for any known genetic based disease.
What does DGP consist of?
Once the embryos are obtained after using the technique of sperm injection into the oocytes (ICSI), we perform a biopsy in a cell of each embryo. The cell is fixed, in order to study the nucleus, then the chromosomes are analysed by being marked with fluorescent probes for those cases in which an aneuploidy is being searched for, while DNA chain amplification is carried out to detect mutations in those cases of monogenic diseases.
Once the healthy embryos are diagnosed, one or two of them will be selected for the transfer into the uterus and the remaining ones will be vitrified in order to use them at a later time.
Thanks to progress in reproductive medicine, and especially in the technique of genetic diagnosis, we can offer our patients the possibility of making their dreams come true by bringing into the world a child free of this illness which he or she would have been doomed to otherwise suffer from.
Monogenic Diseases
Thanks to the most advanced specialized technique in detection of mutation, we can carry out the DGP of any known genetic based illness previously diagnosed on the couple.
Here below are some of the monogenic illnesses that we can diagnose:
Autosomal dominant
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Neurofibromatosis type I
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Myotonic Dystrophy type I (Steinert´s Disease)
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Osteogenesis imperfecta (dominant variant)
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Facio-scapulo-humeral (FSH) muscular dystrophy
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Marfan Syndrome
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Multiple Exostoses
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Hypokalemic Periodic Paralysis
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Von Hippel-Lindaul´s disease
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Huntington Disease
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Familial Amyloidotic Polyneuropathy (FAP)
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Hereditary Angioedema
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Dominant renal Polycystosis
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Cognitive hypertrophic Myocardiopathy
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Pfeiffer Syndrome
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Retinitis Pigmentosa
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Charcot-Marie-Tooth Disease
Autosomal recessive
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Cystic Fibrosis
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Congenital adrenal Hyperplasia (variante recesiva)
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Antley-Bixler Syndrome
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Pompe Disease (or acid maltase deficiency)
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Autosomal recessive renal Polycystosis
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Angelman Syndrome
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Thalassemia
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GM1 Gangliosidoses
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Spinal muscular Atrophy (SMA)
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Falciform Anaemia
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Rhesus Incompatibility Disease
X-linked
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X-fragil Syndrome
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Duchenne muscular Dystrophy (DMD)
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Hemophilia A
