Steinert’s disease (or DM1, myotonic dystrophy type 1) is one of the most common neuromuscular diseases in adults. Its clinical manifestations reflect the involvement of several organs and tissues: the muscle, heart, crystalline lens, endocrine glands, etc. Heart complications make this a very serious condition, with a significant risk of sudden death without prophylactic treatment. This condition is due to abnormal repeats of CTG nucleotide triplets in the non-translated area of the DMPK gene, greater than or equal to 50.
Systematic dried blood stain screening, searching for CTG expansion characteristic of Steinert’s disease, was performed among all newborns in New York State (United States) between December 2013 and April 2014.
An under-evaluated prevalence
Of the 50,382 samples analysed, 24 presented CTG triplet repeats greater than or equal to 50, i.e. 1/2100 newborns, a disease prevalence of 4.8 per 10,000 people, much higher than the figure reported up to now, of 5–20 per 100,000 people.
Especially for the forms with no neuromuscular signs…
More than half (16/24) had a number of repeats between 50 and 150, i.e. genetic abnormalities generally associated with late-onset moderate symptoms, often amounting to early cataract, with no neuromuscular symptoms. However, this does not shield them from heart involvement and/or transmission of a more severe form to their descendants.
… and pre-mutations
A total of 96 samples (1/525) presented a “pre-mutation”, i.e. a number of triplet repeats of between 39 and 50, likely to transform into a pathological abnormality of 50 repeats or more in the next generation.
These results, published in February 2021, emphasize the high prevalence of this common neuromuscular disease, very probably under-diagnosed in routine practice, especially in its forms showing few symptoms.
