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The importance of in-depth genetic analysis in cases of congenital myopathies linked to the RYR1 gene
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On the basis of two paediatric cases of myopathies linked to the RYR1 gene and a review of the literature, a Japanese team has highlighted the complexity of genetic counselling in these diseases, linked to their possible dual mode of inheritance, via an autosomal dominantEn génétique, c’est la caractéristique d’un individu qui n’a besoin que d’un seul exemplaire d’un certain gène (allèle) pour s’exprimer. Cet exemplaire unique peut venir du père ou de la mère. or recessive mode.
- It is difficult to distinguish between these two modes of transmission on the basis of clinical data alone, even though patients with autosomal recessive inheritance present more severe phenotypes.
- Two sporadic cases are described in this publication. The first patient has a de novo missense mutationModification soudaine et transmissible du matériel génétique. Elle peut être spontanée ou induite par des agents dits » mutagènes » (radiations, produits toxiques,…). with autosomal dominant inheritance, while the second has two heterozygous missense mutations, each inherited from one parent with autosomal recessive inheritance.
- The parents were informed of the risk of inheritance in the event of a future pregnancy via genetic counselling (low for the first and not negligible for the second).
- A review of the literature highlights the importance of a complete genomic analysis of all RYR1 coding regions in the patient and his or her parents to improve genetic counselling, particularly in the absence of a family history.
- Prenatal diagnosis may be useful for future pregnancies in cases of autosomal recessive inheritance.
Genetic counselling would be facilitated by the creation of a database enabling each mutation in the RYR1 gene to be correctly assessed, taking into account the mode of inheritance with which they are associated.