Evaluation of a comparative pathogenesis between cancer-associated retinopathy in humans and sudden acquired retinal degeneration syndrome in dogs via diagnostic imaging and western blot analysis

OBJECTIVE: To evaluate dogs with sudden acquired retinal degeneration syndrome (SARDS) for evidence of pituitary gland, adrenal gland, and pulmonary neoplasia and antiretinal antibodies and to evaluate dogs with neoplasia for antiretinal antibodies. ANIMALS: 57 clinically normal dogs, 17 with SARDS, and 53 with neoplasia. PROCEDURE: Thoracic radiography, ultrasonography of adrenal glands, and contrast-enhanced computed tomography of pituitary glands were performed in 15 dogs with SARDS. Western blot analysis was performed on sera of all dogs; recoverin (23 kd) and arrestin (48 kd) retinal antibodies were used as positive controls. RESULTS: Neoplasia was not detected via diagnostic imaging in dogs with SARDS. Western blot analysis revealed bands in all dogs ranging from > 48 to < 23 kd. Prominent bands with equivalent or greater density than 1 or both positive controls at the 1:1,000 dilution, and present at the 1:3,000 dilution, were detected in 28% of clinically normal dogs, 40% of dogs with neoplasia, and 41% of dogs with SARDS. No bands in dogs with SARDS had a consistent location of immune activity, and none were detected at the 23-kd site. The area around the 48-kd site had increased immune activity in all 3 groups. CONCLUSIONS AND CLINICAL RELEVANCE: The etiology of SARDS in dogs does not appear to be similar to cancer-associated retinopathy in humans on the basis of absence of differential antibody activity against retinal proteins. Although dogs with SARDS often have clinical signs compatible with hyperadrenocorticism, neoplasia of the adrenal glands, pituitary gland, or lungs was not detected.