[The significance of boiled-egg fibers in biopsied muscles of neuromuscular disorders].
It is believed that one muscle fiber consists of one fiber type determined by its innervating neuron. In biopsied muscles of Duchenne muscular dystrophy (DMD), however, the author has incidentally found a double-typed fiber which is divided into inner and outer parts. The author termed it a "boiled-egg fiber". The author has examined the appearance rate of the boiled-egg fibers on 682 biopsied muscles obtained from patients with various neuromuscular disorders, and classified the types of the inner and outer parts of the boiled-egg fibers by ATPase staining. Boiled-egg fibers were recognized in 17 cases out of 60 with DMD, 5 out of 146 with other types of muscular dystrophy and 6 out of 94 with myositis. No boiled-egg fiber was found in the remaining 382 cases with other disorders which did not represent necrosis with regeneration of muscle fibers. The total number of boiled-egg fibers was 235 with 192 in DMD and 43 in other disorders. 197 of 235 (83.8%) had the same type for both inner and outer parts and remaining 38 (16.2%) had different types for their inner parts. In 133 of 235 (56.6%), the inner parts were type 2C fibers. Boiled-egg fibers were segmentally found with the length of several hundred micrometers. The above findings suggest that boiled-egg fibers reflect an abnormal regenerating process. It remains to be clarified whether or not inner and outer parts of boiled-egg fibers are double-innervated respectively.
Yamasaki
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Department of Pediatrics, Keio University School of Medicine, Tokyo.
D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D009132:Muscles / Q000473:pathology* / Q000502:physiology; D009136:Muscular Dystrophies / Q000473:pathology* / Q000503:physiopathology; D009468:Neuromuscular Diseases / Q000473:pathology* / Q000503:physiopathology; D012038:Regeneration