Myotonic dystrophy: muscle involvement in relation to disease type and size of expanded CTG-repeat sequence.
This study aimed to: classify a cohort of children and adolescents with myotonic dystrophy (dystrophia myotonica: DM) into congenital and childhood onset forms; estimate CTG expansion size; and quantify muscle strength, contractures, and motor function in children with DM and compare results with those of controls. Participants were clinically examined, medical records were reviewed, and isometric muscle strength, contractures, and motor function were measured. Participants were: 42 children with DM (18 females, 24 males; mean age 8y 9mo [SD 4y 7mo], range 10mo to 17y) and 42 age- and sex-matched, healthy controls. Children with DM were divided into three groups: severe congenital (n=13), mild congenital (n=15), and childhood (n=14). Children with childhood DM were significantly weaker than controls (wrist and ankle dorsiflexors [p=0.0044, p=0.0044 respectively]; hip abductors and flexors [p=0.0464, p=0.0217]; and knee flexors and extensors: [p=0.0382, p=0.0033]). Children with mild congenital DM were significantly weaker than controls in all assessed muscle groups. Contractures and skeletal deformities were more frequent at time of investigation than at birth, suggesting that foot and spine deformities in particular increase over time. Motor function score was significantly lower for children with DM than for controls. Children with severe congenital DM had the lowest motor function, with correlation between motor function and size of CTG repeat (p=-0.743). Children found jumping, heel standing, and head lifting the most difficult items to perform but few had difficulty walking, running, or stair climbing. DM in children is a heterogeneous disorder with a wide spectrum of muscle involvement, and owing to increased risk of contractures and skeletal deformities, regular follow-ups are recommended.
Department of Paediatrics, The Queen Silvia Children's Hospital, Sahlgrenska University Hospital, S-416 85 Göteborg, Sweden. anna-karin.kroksmark@vgregion.se
Anna-Karin
AK
Kroksmark
Anne-Berit
AB
Ekström
Eva
E
Björck
Már
M
Tulinius
D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000302:isolation & purification; D005260:Female; D006801:Humans; D007223:Infant; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009043:Motor Activity / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009223:Myotonic Dystrophy / Q000145:classification / Q000235:genetics* / Q000503:physiopathology; D012720:Severity of Illness Index; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*; D016138:Walking / Q000502:physiology
D004247:DNA