A Finnish retrospective study included data from 137 individuals with distal dominant myopathy, linked to the FINmaj mutation in the TTN gene, followed for 15 years. The results show that:
- the first symptoms appeared before 55 years of age in 109 of them (79.5%) (including five before 35 years of age) and after 55 years of age in the other 28 (20.4%);
- the disease begins on average in the third decade with distal weakness of the lower limbs, which is expressed in the vast majority (97.8%) by difficulties in walking;
- distal muscle weakness becomes significant (testing ≤ 3) only after the age of 40 years; it is significant in all participants from the age of 77 years;
- over 15 years, proximal lower limb muscle strength decreased from 5 to 4 on average on muscle testing and proximal upper limb strength remained at 5 on average;
- on MRI, fatty degeneration of the anterior leg muscles is very marked; it also affects the hamstrings and gluteal muscles after 5 to 10 years of evolution;
- no walking aids were necessary before the age of 62 years;
- no evidence of cardiomyopathy related to distal myopathy was found in this cohort.
Titine et titinopathies. Dossier Mise au point , Cahiers de myologie, 2020, 21 : 9-20
