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Annual Meeting Information

2008 ACVP/AAVLD Diagnostic Travel Award

Robert Johnson, DVM, Purdue University

HYPERTROPHIC OSTEOPATHY ASSOCIATED WITH AN INTRA-ABDOMINAL NEOPLASM IN A CAT. R. Johnson, S. Lenz. Animal Disease Diagnostic Laboratory and Department of Comparative Pathobiology, Purdue University, West Lafayette, IN.

Hypertrophic osteopathy is a hyperostotic syndrome of the appendicular skeleton that is most commonly associated with intrathoracic neoplasia or inflammation. The condition is rarely associated with intra-abdominal lesions. The majority of cases have occurred in dogs and humans, but few have been reported in cats and horses. A 15-year-old, neutered male Domestic Shorthair cat presented for swollen limbs and difficulty in ambulation. Radiographs and gross postmortem examination revealed severe periosteal hyperostosis of the diaphysis and metaphysis of all four limbs, including the humerus, radius, ulna, carpi, metacarpi, femur, tibia, tarsi, metatarsi, and phalanges. The axial skeleton was spared. Hyperostotic lesions were characterized microscopically by lamellar bony trabeculae separated by adipocytes and scant hematopoietic tissue. In several areas, fibrous connective tissue and islands of cartilage were also present. A 2.5 cm x 2.5 cm peri-renal mass compressed the left kidney and adrenal gland. This mass consisted of well-differentiated tubules of cuboidal epithelial cells and was most consistent with a renal tubular adenoma, as mitotic figures were rare and no distant metastases were found. Thoracic pathology was absent. Hyperostosis was most consistent with hypertrophic osteopathy secondary to the suspected renal neoplasm. The pathogenesis of hypertrophic osteopathy is uncertain, but predominant theories include neurogenic or humorally mediated increased circulation to the extremities. Other possible mechanisms include increased levels of humoral or toxic factors that may be produced by neoplastic cells or are abnormally metabolized because of other pathology. Recent literature has also highlighted the potential role of vascular endothelial growth factor and circulating platelets. The mechanism by which this renal tumor caused hypertrophic osteopathy is unknown.

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