Three per cent of couples could be at risk of conceiving babies who are carriers of some type of rare disease

• With advances in genetics, it is now possible to reduce the risk of a future baby suffering from a genetic disease.
• Dr Belén Lledó, Scientific Director at Instituto Bernabeu and Director of IB Biotech: ‘We are all carriers of recessive diseases, and they become a problem when both parents share mutations in the same gene’.
• By studying genetic incompatibilities at Instituto Bernabeu, the transmission of more than 3,000 rare diseases can be prevented.

Recessive diseases are hereditary diseases found in our genetic map. Although they affect only 1% of all newborns, they are mostly serious and incurable diseases and together have a high health, social and emotional impact. ‘We are all carriers of recessive diseases, but this can be a serious problem for our children when both parents share mutations in the same gene,’ explains Dr Belén Lledó, scientific director of Instituto Bernabeu and director of IB Biotech.

According to the expert, if our partner is also a carrier of a mutation in the same gene as us, the risk of our child having the disease caused by that gene is 25%. Furthermore, even if the child is born healthy, the possibility of them being a carrier of the genetic alteration exceeds 50%, which could also have implications for their future offspring.

This genetic reality is often ignored when conceiving, but it is a real risk that affects a wide range of people. ‘Three per cent of couples could be at risk of conceiving babies affected by some type of rare disease associated with genetic mutations, a reality that often goes unnoticed before pregnancy,’ adds the doctor.

Rare diseases are those that affect a small number of people compared to the general population. In the European Union, a disease is considered rare when its prevalence is less than 5 cases per 10,000 inhabitants. In Spain, the Spanish Federation for Rare Diseases (FEDER) estimates that more than 3 million people live with one of these conditions, many of which are genetic in origin and begin in childhood.

More than 70% of rare diseases have a genetic basis, which in many cases is inherited in an autosomal recessive pattern. This means that most parents are unaware that they are carriers until an affected child is born or a specific genetic study is performed. The low individual prevalence of each condition contrasts with the high diagnostic complexity and significant impact they entail, as many result in disability, dependency and the need for specialised healthcare. In this context, preconception screening strategies and genetic counselling play a key role in anticipating risks, facilitating informed reproductive decisions and reducing the incidence of these diseases in offspring.

In this regard, tests such as the Genetic Compatibility Test can help to significantly reduce the risk of transmission of these diseases. This test identifies mutations in the genes responsible for recessive and X-linked diseases. The study of this massive DNA sequencing panel makes it possible to analyse the genes linked to certain diseases.

“This analysis, which we perform on all donor candidates in our molecular genetics laboratory to ensure the safety of each sample, and which we also offer to our patients, reduces the risk of giving birth to a child with one of these diseases from 1 in 100 to 1 in 40,000–50,000, thus minimising the risk of a recessive disease in offspring,” says Dr Belén LLedó. Genetic compatibility testing is recommended even for couples with no family history, as most carriers are unaware of their condition. Prevention, therefore, is not only aimed at cases of obvious risk, but also at the general population who wish to plan their parenthood with as much information as possible.

This test is recommended for couples who want to conceive naturally or through assisted reproduction treatment, especially if one or both partners have a family history of or are carriers of a genetic disease, or if they are related by blood, as in this case they will have a higher risk of sharing mutations in the same gene. It is a simple procedure that is performed through a blood or saliva test, with results available in 15 days.

If genetic incompatibilities are found in the couple, it is possible to prevent transmission of the disease using techniques such as in vitro fertilisation (IVF), transferring only embryos that are free of the disease.

More than 3,000 diseases

Researchers at Instituto Bernabeu’s molecular genetics laboratory have developed the most comprehensive genetic study (extended TCG), a panel of more than 3,000 recessive diseases that analyses 2,306 genes. The most common are cystic fibrosis, non-syndromic deafness, thalassaemia, spinal muscular atrophy, phenylketonuria and Gaucher disease.

This comprehensive study covers all the diseases that the SEF (Spanish Fertility Society) recommends analysing in any pre-conception genetic study.

Instituto Bernabeu offers a specialised genetic counselling service that provides comprehensive care to anyone who requires a detailed analysis of their genome for any reason. This type of testing allows patients to access crucial information about their genetic profile, which can be essential for the diagnosis, treatment and prevention of various diseases. In addition, these genetic tests offer significant benefits, such as the personalisation of medical treatments according to individual genetic profiles and family planning informed by genetic risks.

We could include a message such as this: On Rare Disease Day, experts emphasise the importance of genetic prevention as a key tool for reducing new cases and moving towards more predictive and personalised medicine.