Skeletal remains of five blue foxes (Vulpes lagopus) from St. Paul Island, Pribilof Islands, Alaska: A view of differential diagnosis

We evaluated skeletal remains of five blue arctic foxes from St. Paul Island, Pribilof Islands, Alaska. All five had been found dead. Cleared skeletal remains were examined visually and by magnification or backlighting where necessary. Pathological features were described and photographed. Results suggested that more than one disorder may have occurred in these foxes, with primary observations being demineralizing and/or proliferation. Most prominently affected were the skull, maxillae, mandibles, pelvis, long bones, and major diarthrodial joints. It was critically important to recognize certain other pathological features that can be observed on many or most fox skeletal remains but are unlikely to relate to conditions that demineralize bone or cause overt bone loss, multifocal loss of joint architecture, or severe multifocal periarticular boney proliferation. The differential diagnosis of canid skeletal demineralizing includes primary and secondary (nutritional or renal) hyperparathyroidism. Boney proliferation has a wider differential spectrum that can include hypervitaminosis A, osteomyelitis, abnormalities related to inbreeding, and environmental toxicosis. In our view, given the lack of soft tissue for histological evaluation and biochemical analysis, a well-considered differential diagnosis is an appropriate scientific point of conclusion. In the many similar circumstances that would require additional studies for valid definitive diagnosis during life, investigators should review relevant literature and consider the value of well-structured differential diagnosis, as contrasted with more speculative definitive diagnoses.