Heterotopic Ossification of the Soft Tissues Overlying the Carpal Bones of a 2-year-old Bearded Dragon (Pogona vitticeps)

A 2-year-old female bearded dragon (Pogona vitticeps) presented to the clinic exhibiting lameness and significant swellings bilaterally in the carpal region. On physical examination the lizard was determined to be in obese body condition and pododermatitis was observed on the palmar aspects of both carpi. The rest of the examination was unremarkable. Radiographs revealed opacities present in both carpal joints with possible fluid accumulation. Biochemistry revealed hypercalcemia and hyperphosphatemia. A joint aspirate was performed and submitted for cytology and culture. The sample was sterile and only inflammatory cells were seen. Despite these results, the swelling initially improved with daily lincomycin 5 mg/kg IM but recurred after one month, and the lizard was referred to a specialist center for further investigations. A tissue biopsy was performed and submitted for histology and culture. Histopathologic examination revealed periarticular soft tissue ectopic bone characterized by a proliferation of ectopic cartilage and both lamellar and woven bone with haematopoietically active bone marrow within a fibrous connective tissue stroma. Bacterial culture revealed a scant growth of Staphylococcus aureus and Serratia marcescens. The lizard received ceftazidime 20 mg/kg every 72 hours IM for three weeks. Clinical signs resolved until eight months later when the swellings returned.