Also known as: Hypertrophic Pulmonary Osteopathy — Hypertrophic Pulmonary Osteoarthropathy — HO — Marie's Disease
Introduction
This is a rare condition that occurs in all species.
It is a diffuse, periosteal proliferative condition of long bones secondary to neoplastic or infectious masses in the thoracic or abdominal cavity, including tuberculosis, pulmonary neoplasia, granulomatous pleuritis and granulomatous lymphadenitis of the mediastinal lymph nodes.
The exact pathogenic mechanism is unknown, but several theories have been proposed:
- 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.
- 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 an increased blood flow and the periosteal reaction. Regression of the bony lesions after a vagotomy has been demonstrated.
Clinical Signs
Animals will show lameness, long bone pain, and may have swelling in one or usually several limbs.
They may also have signs relating to their primary condition, such as dyspnoea, coughing, dysphagia, pyrexia, lethargy.
Diagnosis
Radiography is the method of choice for diagnosing the condition, as it usually reveals the primary mass and the peripheral bone reactions.
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.
Histologically, there is hyperaemia of the periosteum, deposition of new bone and the width of the cortex may double in a few weeks.
Treatment
Removal of the thoracic or abdominal mass will lead to a regression of the bony changes.
The prognosis is variable depending on the primary mass, but may be poor if the mass is neoplastic and aggressive.
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Small Animal Orthopaedics Q&A 12 |
References
Merck and Co (2008) The Merck Veterinary Manual Merial
King, L. (2004) Textbook of respiratory diseases in dogs and cats Elsevier Health Sciences
Morgan, J. (1999) Radiology of veterinary orthopaedics Wiley-Blackwell
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