Muscle phenotype in patients with myotonic dystrophy type 1.

Grete Andersen, Mette C Ørngreen, Nicolai Preisler, Eskild Colding-Jørgensen, Torben Clausen, Morten Duno, Tina D Jeppesen, John Vissing

Neuromuscular Research Unit, Department of Neurology, 3342, Rigshospitalet Blegdamsvej 9, DK-2100, Copenhagen, Denmark. grete.andersen@rh.dk

Muscle & nerve 2013 Mar

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The pathogenesis of muscle involvement in patients with myotonic dystrophy type 1 (DM1) is not well understood. In this study, we characterized the muscle phenotype in patients with confirmed DM1. In 38 patients, muscle strength was tested by hand-held dynamometry. Myotonia was evaluated by a handgrip test and by analyzing the decrement of the compound muscle action potential. Muscle biopsies were assessed for morphological changes and Na(+)-K(+) pump content. Muscle strength correlated with a decline in Na(+)-K(+) pump content (r = 0.60, P < 0.001) and with CTG expansion. CTG expansion did not correlate with severity of myotonia, proximal histopathological changes, or Na(+)-K(+) pump content. Histopathologically, we found few centrally placed nuclei (range 0.2-6.9%). The main findings of this study are that muscle weakness correlated inversely with CTG expansion and that central nuclei are not a prominent feature of proximal muscles in DM1. Copyright © 2012 Wiley Periodicals, Inc., a Wiley company.

Citation

Grete Andersen, Mette C Ørngreen, Nicolai Preisler, Eskild Colding-Jørgensen, Torben Clausen, Morten Duno, Tina D Jeppesen, John Vissing. Muscle phenotype in patients with myotonic dystrophy type 1. Muscle & nerve. 2013 Mar;47(3):409-15