Résumé :
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Background: A number of patients with molecularly confirmed DM2 diagnosis proved to have had fybromialgia as their previous diagnosis. It seems possible that some families with DM2 phenotype have neither mutation. Objectives: To show how a myotonic dystrophy type 2 may have been missed in patient with fibromyalgia and how muscle biopsy may be useful to the diagnosis of DM2. Patient/Methods: A 63 year-old Spanish woman with healthy non-consanguineous parents had presented with widespread muscle-skeletal pain with onset al 45 years of age and with a mild and non-progressive proximal upper limbs weakness. The osteotendinous reflexes were present and she presented a slight atrophy of thigh muscles with rather bulky calves. Absence of clinical myotony. Repeated CK levels were elevated 1 to 8 folds. There was no facial muscles, cardiac, hepatic or CNS, involvement, The diagnosis considered was Fibromyalgic Syndrome of unknown aetiology. The electrophysiological study showed myogenic patterns and abundant myotonic discharges. The electrophysiological study of the patient’s daughter, who presented some muscle-skeletal pain and a minimal proximal upper limbs paresis without clinical myotony, showed abundant myotonic discharges. Results: Lower limb CT Scan showed a minimal atrophy in proximal muscles; the leg muscles were not atrophic but a slightly hypodense pattern was found in deep posterior compartments. Muscle biopsy (deltoid) showed various morphological alterations: Nuclear changes, pycnotic nuclear clumps, angular atrophic fiber, great predominance of type 1 fibers and selective and preferential type 2B fiber atrophy in contrast to type fiber 1 atrophy in DM1 patient. Search for the molecular defect on DM1 and DM2 genes resulted negative. Conclusions: The results of this study confirm that there are patients with DM2 disease phenotypes among fibromyalgic patients due to similar clinical symptoms. Muscle biopsy may be useful to the diagnosis of DM2.
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