A new technique developed at a Galician clinic (Galicia, Spain) enabled in 2010 the birth of a child free from retinitis pigmentosa (RP), an eye disease that causes blindness because of inherited retinal degeneration. This was the first time that the transmission of a disorder linked to the X chromosome was prevented in Spain.
What is it?
Retinitis pigmentosa (RP) is the most common cause for inherited retinal degeneration. It causes the degeneration of the photoreceptors, provoking blindness in a great number of cases. It is estimated that around 25,000 people in Spain are affected with RP.
Is it hereditary?
Severe vision loss does not affect everybody equally, including members of the same family. For this reason, in some cases, offspring are more seriously affected than parents or, conversely, there are elderly individuals whose visual acuity is considered as normal for their age.
RP has several patterns of inheritance. One of them, despite it is one of the most uncommon ones, is the pattern linked to the X chromosome (it occurs in between 1-10% of cases). In this case, women are the carriers of the disease who transmit it to their male offspring.
Fertility and pregnancy
To date, couples in which the mother suffered from RP could get pregnant and give birth to healthy daughters thanks to assisted reproductive treatments, which helped choosing the baby’s gender by transferring only female, non-carriers of RP embryos.
This new technique allows these women to have male children non-affected by this mutation and, therefore, free from RP. By applying this new technology, a female carrier of RP gave birth to her first male son, who was free from the disease.
The technique is known as “quick” genotyping of embryos. It consists of identifying among the embryonic cells the mutation that causes RP. By doing this, we will be able to separate the healthy embryos from the unhealthy ones. Thus, only healthy embryos will be transferred to the maternal womb, regardless their gender. This means that in families where the woman is a carrier of RP, the transmission chain would break after giving birth to a non-affected son.