Hypertrophic osteopathy: A retrospective case control study of 30 dogs

Hypertrophic osteopathy (HO), mostly described in dogs with thoracic neoplasia, is characterized by pathologic periosteal new bone formation (PNBF). This study compared 30 dogs with HO with 101 age- and primary lesion-matched negative controls. Boxers were overrepresented in the HO group compared to mixed breeds. HO-related clinical signs preceded or appeared concurrently with the primary disease signs in 85% of the dogs. Pyrexia, regional lymphadenopathy, warm and swollen limbs and joints and nasal hyperkeratosis were significantly (P≤0.015) more frequent in the HO group compared to the controls. Mean platelets count and frequency of thrombocytosis and schistocytosis were also significantly (P≤0.012) higher in the former. Anemia and leukocytosis were common in both groups. All HO-dogs showed increased alkaline phosphatase (ALP) activity, which was higher (P=0.042) compared to the controls. Te HO-related PNBF involved the metacarpi or metatarsi (76%), distal and proximal long bones (66% and 38%, respectively), carpi or tarsi (31%) and phalanges (21%).Te HO-associated primary lesions included esophageal mass (33%), likely due to the high prevalence of spirocercosis in Israel, metastatic lung disease (27%), primary pulmonary mass (20%) and thoracic wall masses (13%). Te median survival time of the HO dogs was 24 days (range 1-117). Presence of macroplatelets, thrombocytosis and schistocytosis in HO dogs support the hypothesized pathophysiology of human HO. This is the first case-control study of canine HO, and the second to describe its clinical and laboratory findings in a relatively large number of dogs.