Physical function and mobility in children with congenital myotonic dystrophy

Abstract

Introduction Congenital Myotonic Dystrophy (CDM) occurs when symptoms of myotonic dystrophy present at birth. This study evaluated the relationship between physical function, muscle mass, and age to provide an assessment of the disease and help prepare for therapeutic trials. Methods CDM participants performed timed functional tests (TFTs), The first 2 minutes of the 6-minute walk test (2/6MWT), myometry, and dual-energy x-ray absorption (DEXA) scans. Healthy controls (HC) performed TFTs, 6MWT, and myometry. Results Thirty-seven children with CDM and 27 HC, ages 3-13, participated. There were significant differences in the 10-meter walk (11.3s in CDM vs 6.8s in HC) and 2MWT (91m in CDM vs 193m in HC). DEXA lean mass of the right arm correlated with grip strength (r=0.91), and lean mass of right leg with 6MWT (r=0.62). Conclusion Children with CDM have significant limitations in strength and mobility. The tests performed were reliable, and lean muscle mass may serve as a useful biomarker.

Body composition in patients with congenital myotonic dystrophy

“…In conclusion, in follow‐up to our previous work in which we showed that DXA measures of regional muscle mass correlate well with motor strength and function testing, we now show that the muscle mass of patients with CDM improves almost to normal compared with healthy, age‐matched controls. This corresponds to what is seen clinically in children with CDM over time.…”

“…The measurement of LBM has the potential to be an important biomarker to reflect muscle mass and, ultimately, functional strength in this population. As a surrogate for muscle strength, it appears to have some value as it correlated well with functional measures such as the 6‐minute walk test and 10‐meter walk/run test in a previous study by our group; where we also demonstrated that older children have higher muscle mass, however, we did not compare this improved muscle mass to age‐matched controls or typically developing children …”

“…In recent studies, it has been shown that patients with CDM have lower scores in physical functional tests (10‐m walk, time to run 10 m, time to climb 4 stairs, time to rise from the floor. and 6‐min walk test) compared with healthy individuals; however, by the age of 12–14 years, they have outcomes that are similar to those of healthy controls . Although most patients with CDM have a global developmental delay, the vast majority achieve ambulation at a mean age of 2.4 years, varying from 1.2 to 3.9 years .…”

“…The pathophysiology suggests that CDM may be a disorder of muscle immaturity, with the splicing dysfunction forcing proteins into more fetal isoforms . Both clinical observation and the pathophysiology suggest that one might see a gradual improvement in muscle mass (relative to their peers) as the child ages …”

“…and 6-min walk test) compared with healthy individuals; however, by the age of 12-14 years, they have outcomes that are similar to those of healthy controls. 3 Although most patients with CDM have a global developmental delay, the vast majority achieve ambulation at a mean age of 2.4 years, varying from 1.2 to 3.9 years. 4 The pathophysiology suggests that CDM may be a disorder of muscle immaturity, with the splicing dysfunction forcing proteins into more fetal isoforms.…”