Calcinosis Circumscripta in the Digital Extensor Tendon of a Tawny Eagle (Aquila rapax)

A 9-month-old, captive-bred, female tawny eagle (Aquila rapax) presented with a nonpainful, firm, nodular structure attached to the digital extensor tendon. The mass was surgically resected without complications and was submitted for histopathologic examination. Grossly, cut surfaces of the lesion had chalky-white deposits. Histologically, the resected tissue was identified as calcinosis circumscripta. No recurrence was observed in follow-up after 6 and 12 months. To our knowledge, this is the first case of calcinosis circumscripta in a bird involving a limb extremity, similar to the presentation recognized more commonly in domestic animals. Calcinosis circumscripta should be included in the differential diagnosis list for nodular masses attached to the tendons in birds.