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Muscles Developmental - Pathology (view source)

Revision as of 20:07, 18 August 2008

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===Congenital diaphragmatic defects===
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*Clefts may lead to [[Peritoneal cavity - developmental#Pleuroperitoneal diaphragmatic hernia|herniation]] of abdominal organs into thoracic cavity in any species
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===Myofibrillar hypoplasia===
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*In piglets
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* = '''Splayleg'''
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*May spontaneously resolve
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*Unknown cause
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*Responsible for significant deaths
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===Hyperplasia of muscle fibres===
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*In calves and lambs
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*'''“Double muscling”'''
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**Increased number of myofibres in affected muscle (thighs, rump, loin)
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**Predisposes to dystocia
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===Muscular dystrophies===
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*Inherited group of degenerative muscular diseases
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*Progressive muscle weakness and wasting
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*Usually due to a genetic fault -> muscular protein deficiency
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**Duchenne MD in humans due to dystrophin deficiency also present in some animals
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**Dystrophin gene mutations reported in the Golden Retriever, Rottweiler, German shorthaired pointer and Irish terrier ''etc.''
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*Inadequate [[Muscles - normal#Regeneration|regeneration]], [[Muscles - hyperplastic and neoplastic#Hypertrophy|compensatory hypertrophy]]
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*More about [[Muscular dystrophy]]
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===Glycogen storage diseases===
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*Caused by a deficiency of an enzyme
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*See [[General Pathology - Degenerations and Infiltrations#Glycogen infiltration|general pathology]]
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*Type II glycogenosis
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**Deficiency of acid maltase
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**In Shorthorn cattle
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**Muscular weakness and incoordination
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**Glycogen stored in skeletal muscle, heart and CNS
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**Type I and II muscle fibres contain glycogen vacuoles
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*Type III glycogenosis
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**Deficiency of debranching enzyme
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**In dogs
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**Causes [[Myocardial - Pathology#Hypertrophic cardiomyopathy|hypertrophic cardiomyopathy]] and hepatomegaly
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**Glycogen in skeletal and cardiac muscle, neurons nad hepatocytes
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===Steatosis===
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*Also called '''lipomatosis'''
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*In cattle, sheep and pigs
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*Fat replaces lost muscle fibres
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*Pale muscle, bilaterally symmetrical
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*No clinical significance
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*Noticed at slaughter or necropsy
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===Myasthenia gravis (MG)===
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*'''Acquired'''
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**Autoimmune disease
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***Antibodies directed against acetyl choline receptors
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**Associated with [[Lymphoreticular/Haemotopoietic system - general pathology#Tumours of the Thymus|thymomas]], [[Oesophagus#Congenital Achalasia - Megaoesophagus|megaoesophagus]] and dysphagia
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**In adult dogs
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*'''Congenital'''
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**Inherited deficiency in acetyl choline receptors
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**Rare
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**Newfoundland, Jack Russel Terrier, Springer Spaniels – genetic predisposition
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**In dogs – 4 DLA genes recognized: DLA-12, DLA-88, DLA-79 and DLA-64
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**Associated with HLA gene in humans
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**No antibodies against acetyl choline receptors in serum
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**Non-specific muscle [[Muscles - degenerative#Atrophy|disuse atrophy]] and fibrosis or no changes on histology
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*Both forms manifest as weakness which worsens on exercise
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===Canine dermatomyositis===
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*Hereditary in Collies and Shetland sheepdgs
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*Lesions resemble [[Muscles - inflammatory#Canine polymyositis|canine polymyositis]]
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*Also degeneration of blood vessels -> muscle [[Muscles - degenerative#Ischaemia|microinfarcts]]
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*Usually generalised but temporalis may be involved the most
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*Also involves [[Skin Immunologic - Pathology#Dermatomyositis|skin]]
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===[[Muscles - degenerative#Porcine stress syndrome|Porcine stress syndrome]]===
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