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*Also called '''hypertrophic pulmonary osteopathy'''
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Also known as: '''''Hypertrophic Pulmonary Osteopathy — HO — Marie's Disease'''''
*In '''all species'''
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*Associated with chronic lesions (intrathoracic neoplasm or space-occupying lesion) usually in the thorax
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==Introduction==
**[[Respiratory Bacterial Infections - Pathology#Tuberculosis|Tuberculosis]]
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This is a '''rare condition''' that occurs in '''all species'''.
**[[Pulmonary Neoplasia|Pulmonary neoplasia]]
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**[[Pleuritis|Granulomatous pleuritis]]
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It is a '''diffuse, periosteal proliferative condition''' of long bones secondary to '''neoplastic or infectious masses''' in the thoracic or abdominal cavity, including [[Respiratory Bacterial Infections - Pathology#Tuberculosis|tuberculosis]], [[Pulmonary Neoplasia|pulmonary neoplasia]], [[Pleuritis|granulomatous pleuritis]] and granulomatous lymphadenitis of the mediastinal lymph nodes.
**Granulomatous lymphadenitis of mediastinal nodes
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*Grossly:
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The exact pathogenic mechanism is unknown, but several theories have been proposed:
**Periosteal proliferation of bone on '''diaphyses''' of distal limbs
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:'''Humoral theory''': there may be right-to-left shunts associated with pulmonary neoplasia, that lead to platelet clumps and megakaryocytes circumventing the vasculature of the lungs and migrating to the periphery. Once there, platelets produce '''Platelet-Derived Growth Factors''' which induce increased vascular permeability which alters fibroblasts and inflammatory cells and results in the periosteal reaction seen with HO.
**Progressive and bilateral
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:'''Neuronal theory''': the vagus nerve is stimulated by neural reflexes produced by thoracic tumours, and it then stimulates fibres in the distal limbs. This leads to and '''increased blood flow''' and the periosteal reaction. Regression of the bony lesions after a vagotomy has been demonstrated.
*Histologically:
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**Hyperaemia of periosteum
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==Clinical Signs==
**Deposition of new bone
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Animals will show '''lameness, long bone pain''', and may have swelling in one or usually several limbs.
**Width of cortex may double in a few weeks
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*Postulated to be due to stimulation of vagus by intrathoracic lesion -> increasing blood floow to extremities -> thickening of periosteum
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They may also have signs relating to their '''primary condition''', such as dyspnoea, coughing, dysphagia, pyrexia, lethargy.
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==Diagnosis==
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'''Radiography''' is the method of choice for diagnosing the condition, as it usually reveals the primary mass and the peripheral bone reactions.
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The peripheral reaction appears as a periosteal reaction with '''new trabecular bone''' perpendicular to and continuous with the cortical surface. New bone may also form in the '''soft tissues''' away from the cortex.
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Histologically, there is hyperaemia of the periosteum, deposition of new bone and the width of the cortex may double in a few weeks.
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==Treatment==
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'''Removal of the thoracic or abdominal mass''' will lead to a regression of the bony changes.
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The prognosis is '''variable''' depending on the primary mass, but may be poor if the mass is neoplastic and aggressive.
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{{Learning
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|flashcards = [[Small Animal Orthopaedics Q&A 12]]
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}}
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==References==
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Merck and Co (2008) '''The Merck Veterinary Manual''' ''Merial''
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King, L. (2004) '''Textbook of respiratory diseases in dogs and cats''' ''Elsevier Health Sciences''
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Morgan, J. (1999) '''Radiology of veterinary orthopaedics''' ''Wiley-Blackwell''
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[[Category:To Do - Helen]]
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[[Category:To Do - Review]]
    
[[Category:Bones - Hyperplastic Pathology]]
 
[[Category:Bones - Hyperplastic Pathology]]
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