Founded in 2021, our association brings together families living with MYT1L syndrome and the professionals committed to supporting them. A rare genetic disease, still little known — but one for which every year brings new progress.

 

MYT1L syndrome — what you need to know

MYT1L syndrome is a rare genetic neurodevelopmental disorder caused by an alteration (mutation or deletion) of the MYT1L gene, located on chromosome 2p25.3 (Orphacode 647799). It can be inherited from a carrier parent, or occur spontaneously with no family history (de novo).

• Everyone who carries this genetic alteration will develop manifestations, but their severity varies greatly from one person to another: profiles range from mild support needs to multiple disabilities.

• The first signs appear from the neonatal period or early childhood, as a global developmental delay primarily affecting language.

• These are followed, to varying degrees, by: learning difficulties, intellectual disability, neurodevelopmental disorders (ASD, ADHD), behavioural difficulties, overweight or eating disorders (including hyperphagia), sleep disorders, epilepsy in some cases, and non-specific brain MRI abnormalities.

• The condition is non-degenerative.

• There is currently no specific treatment.

• Management is multidisciplinary, as early as possible, and continues throughout life — medical, paramedical, medico-social and educational.

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What has been built in less than five years:

• Official recognition (Orphanet 647799, 2023) and a National Diagnostic and Care Protocol (PNDS) for MYT1L syndrome, developed with Dr Juliette Coursimault, lead clinical geneticist at Rouen University Hospital, and published by the Haute Autorité de Santé in February 2026 — a national reference now binding on all healthcare professionals.

• A strong foothold within the French healthcare system: Dr Coursimault works within the Rare Disease Reference Centre (CRMR) for Developmental Anomalies and Malformative Syndromes at Rouen University Hospital — a constitutive centre for the North-West inter-region, affiliated with the AnDDI-Rares health network.

• Active international scientific collaborations: in Germany with the teams of Dr Moritz Mall and Prof Maja Hempel in Heidelberg, and in the United States with those of Dr Granadillo de Luque and Dr Dougherty in Saint Louis.

• A growing international patient network: The MYT1L Project Foundation in the United States (2024) and the association ExtraValientes MYT1L in Spain (2025).

• Recognition within the patient advocacy community: member of the Alliance Maladies Rares, France's leading collective dedicated to rare diseases.

• A publicly recognised non-profit organisation (association reconnue d'intérêt général) — donations are eligible for a 66% tax relief for individuals and 60% for companies under the French corporate philanthropy scheme.

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What drives us

• Know more to understand better.

• Understand better to support better.

• Support better to open up new possibilities.

In practice: raising awareness of the syndrome, supporting families at every stage and in every area of life, fostering the sharing of experience and encouraging research.

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What we believe

No one should face this disease alone.

Knowledge is advancing. So is cooperation.

And it is together — families, clinicians, researchers — that new perspectives open up.