No abstract

A 12-year-old Irish sports horse gelding presented with a recently developed oval firm mass at the plantaromedial aspect of right tarsus, located between the gastrocnemius and deep digital flexor tendon. At presentation, the horse was mildly right hind lame, with no exacerbation with flexion. Radiography and ultrasonography revealed an ovoid mineralised mass within soft tissues plantaromedially to tarsus and distal tibia and not associated with tarsal sheath or calcaneal bursa. Due to mild intermittent lameness and concerns regarding possibility for further increase in size, the horse underwent en bloc removal of the calcified mass under general anaesthesia. Histopathology showed the mass contained fibrous reactive connective tissue, undergoing bone and cartilage metaplasia and degeneration, with a central area of calcified bone and surrounding region of mononuclear inflammation. These characteristics although reminiscent of calcinosis circumscripta were diagnosed as focal dystrophic calcification. The horse made a full recovery and returned to a normal exercise level.