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Progressive myotonia in foals resembling human dystrophia myotonica
Author(s) -
Reed Stephen M.,
Hegreberg Gerald A.,
Bayly Warwick M.,
Brown Christopher M.,
Paradis Mary R.,
Clemmons Roger M.
Publication year - 1988
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880110403
Subject(s) - myotonia , medicine , myotonic dystrophy , atrophy , amyotrophy , electromyography , muscle hypertrophy , anatomy , weakness , pathological , sarcoplasm , external ophthalmoplegia , exercise intolerance , myopathy , pathology , biology , heart failure , calcium , physical medicine and rehabilitation , biochemistry , mitochondrial dna , gene
Abstract A severe and progressive neuromuscular disorder accompanied by clinical, electrophysiological, and pathological features resembling human dystrophia myotonica was observed in three foals. This disorder was apparent as early as 1 month of age and involved progressive skeletal muscle dysfunction, initially characterized by proximal muscle hypertrophy and hypertonicity with subsequent muscle stiffness, weakness, and atrophy. Multisystem involvement was manifested in one case by testicular hypoplasia, early cataract formation, and borderline glucose intolerance. Prolonged dimpling of these large rear‐limb muscles was elicited by percussion. Myotonic discharges were identified by electromyography. Percussion dimpling and the typical myotonic discharges persisted after neuromuscular blockade. Distinctive histologic muscle changes included ring fibers, sarcoplasmic mass formation, variation in fiber diameter size, and internally positioned nuclei.