A probable Finnish founder effect in a form of congenital myasthenic syndrome

Finnish researchers report the clinical and biological data of 15 patients from 14 unrelated, non-consanguineous families diagnosed with congenital myasthenic syndrome (CMS) linked to the DOK7 gene:

• all were homozygous carriers of a mutationModification soudaine et transmissible du matériel génétique. Elle peut être spontanée ou induite par des agents dits » mutagènes » (radiations, produits toxiques,…). in the DOK7 gene (c.1508dupC),
• this was accompanied by considerable variability in phenotypic expression,
• the authors distinguished between two groups, one paediatric (6 patients) and the other with onset of symptoms in adulthood (9),
• misdiagnosis was the rule in adults, especially as the decrement could be absent on EMGTracé rendant compte de l’activité électrique produite par la contraction musculaire, enregistré à l’aide d’une aiguille fine implantée dans le muscle. Il permet de savoir si le problème musculaire est dû à une atteinte des muscles ou à une atteinte des nerfs..

This form linked to the DOK7 gene appears to be by far the most common form of MSC in Finland.

Homozygosity of a Founder Variant c.1508dupC in DOK7 Causes Congenital Myasthenia With Variable Severity. Palmio J, Kiviranta P, Hartikainen PH et al.Neurol Genet. 2024 May 7;10(3):e200155.