Signalment & History
A 7 year old MN Border Collie presents for intermittent lameness of the right thoracic limb.
Findings
Along the lateral and palmar aspects of the fifth metacarpal bone and the caudal aspect of the distal ulnar diaphysis there is a well-defined, solid, continuous, mildly irregularly marginated periosteal proliferation. The soft tissue surrounding these regions are mildly thickened. Three view thoracic radiographs are obtained.
There is a soft tissue opaque nodule in the ventral aspect of the right caudal lung lobe measuring 5.5 cm. The tracheal and main bronchial walls are mineralized. The cardiovascular structures, mediastinum and pleural space remains normal. On the ventrocaudal aspect of the thoracic wall, there is a fat opaque broad-based mass measuring 3.6 cm. Along the ventral aspect of the thoracic and thoracolumbar vertebral bodies, there is moderate spondylosis deformans. In the caudal aspect of the glenoid cavities and humeral heads, mild osteophyte formation is identified.
Diagnosis
This patient is diagnosed with non-aggressive periosteal proliferation of the right fifth metacarpal bone and distal ulna. These changes are likely due to the presence of the primary pulmonary mass, with bronchial adenocarcinoma considered most likely.
Conclusions
Hypertrophic Osteopathy (HO)
- Generalized osteoproductive disorder of the periosteum
- Affects long bones of the extremities
- Usually caused by cardiopulmonary disease or neoplasia
- When neoplasia is involved, pulmonary neoplasms are most likely
- Reported in animals with intraabdominal neoplasia (urinary neoplasia most often associated)
- Pathogenesis not clearly understood
- Proposed that release of VEGF and PDGF are involved
- Affected animals have increased blood flow to extremities
- Overgrowth vascular connective tissue
- Fibrochondroid metaplasia
- Subperiosteal new bone formation
- New bone formation typically begins on digits then extends toward the axial skeleton
- When joints are involved, large perichondral osteophytes form
References
Allan GS. Radiographic Signs of Joint Disease in Dogs and Cats. In: Thrall, ed. Textbook of Veterinary Diagnostic Radiology. 6th ed. St. Louis: Elsevier; 2013. p. 344.
Withers SS, Johnson EG, Culp WTN, et al. Paraneoplastic hypertrophic osteopathy in 30 dogs. Veterinary and comparative oncology 2013;13:157-165
