Muscle weakness in children with neurofibromatosis type 1.
OBJECTIVE
To investigate if children with neurofibromatosis type 1 (NF1) have reduced muscle strength compared with children with typical development.


METHODS
Maximal isometric strength of 15 upper and lower limb muscle groups was evaluated in 30 children with NF1 (16 males, 14 females; aged 4-16y) and 30 age-, sex-, height-, and weight-matched controls using hand-held dynamometry by a single evaluator. Both the left and right sides were assessed.


RESULTS
Children with NF1 were significantly weaker than children with typical development across all 15 muscle groups assessed (p<0.05). Apart from elbow flexion, there were no differences between the left and right sides (p>0.05). Magnitude of differences between the children with NF1 compared with the controls ranged from 3% to 43%. Males and females were equally affected.


CONCLUSIONS
This study shows that children with NF1 have reduced muscle strength compared with children with typical development. This muscle weakness is present from the earliest stages of the disease assessed and persists throughout childhood with no sex difference. These results support recent evidence from mouse studies that NF1 is associated with a primary myopathy.
Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, NSW, Australia.|Arthritis and Musculoskeletal Research Group, Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
Kayla M D
KM
Cornett
Murdoch Children's Research Institute, Melbourne, Vic., Australia.|Department of Paediatrics, Faculty of Medicine, University of Melbourne, Melbourne, Vic., Australia.
Kathryn N
KN
North
Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, NSW, Australia.|Arthritis and Musculoskeletal Research Group, Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
Kristy J
KJ
Rose
Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, NSW, Australia.|Arthritis and Musculoskeletal Research Group, Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.|Murdoch Children's Research Institute, Melbourne, Vic., Australia.|Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospital Network (Randwick and Westmead), Sydney, NSW, Australia.
Joshua
J
Burns
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009456:Neurofibromatosis 1 / Q000150:complications* / Q000503:physiopathology