Type II muscle fibers atrophy associated with silent corticotroph adenoma in a dog.
The Silent Corticotroph Adenoma (SCA) is a pituitary adenoma variant characterized by the immunoreactivity for adrenocorticotropic hormone (ACTH) and related peptides, without the clinical signs of Cushing's disease. SCA has been postulated to either secrete structurally abnormal ACTH that is inactive but detectable by immunohistochemistry or radioimmunoassay, or to secrete ACTH intermittently or at low levels continuously. Excess of ACTH has been associated to type II muscle atrophy. We describe a case of type II muscle fibers atrophy associated with silent corticotroph adenoma in a dog. The dog showed moderate to severe proximal muscle wasting and weakness with normal levels of muscle-associated enzymes. In the limb muscle biopsies, type II fibers were uniformly smaller than type I fibers. In temporalis muscles, there were few atrophic fibers, and several irregular areas of loss of enzymatic activity observed in NADH, SDH and COX stains. The tumour showed a trabecular growth pattern and immunohistochemical analysis demonstrated the presence of cytoplasmic immunoreactivity for ACTH. The muscle atrophy was considered to be related to an excess of inactive ACTH. Studying spontaneous occurring rare diseases in animals could help to understand the mechanism of similar diseases in human has well.
Department of Pathology and Animal Health, Laboratory of Comparative Neuromuscular Diseases, University of Naples Federico II, via Delpino, 1 80137 Naples - Italy.
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D049913:ACTH-Secreting Pituitary Adenoma / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D000324:Adrenocorticotropic Hormone; D000818:Animals; D004283:Dog Diseases / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D004285:Dogs; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology / Q000662:veterinary*; D009246:NADH Tetrazolium Reductase / Q000378:metabolism; D010911:Pituitary Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000662:veterinary*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011863:Radioimmunoassay / Q000662:veterinary; D013194:Staining and Labeling / Q000379:methods / Q000662:veterinary; D013385:Succinate Dehydrogenase / Q000378:metabolism
D000324:Adrenocorticotropic Hormone; D011451:Prostaglandin-Endoperoxide Synthases; D013385:Succinate Dehydrogenase; D009246:NADH Tetrazolium Reductase