Osteochondrodysplasia in a Scottish Fold Cat Treated with Radiation Therapy and Samarium-153-1,4,7,10-Tetraazacyclododecane-1,4,7,10-Tetramethylene-Phosphonic Acid.

Osteochondrodysplasia is a painful, progressive clinical syndrome unique to Scottish fold cats because of a heritable missense mutation in the TRPV4 gene. An 8 yr old male neutered Scottish fold cat was presented for a mass on his hind paw. The mass caused decreased mobility in the metatarsal region and digits and resulted in significant discomfort. Because of extensive skeletal abnormalities attributed to breed-related osteochondrodysplasia, the owner was reluctant to pursue amputation. Radiation therapy was pursued for palliation of pain. After coarsely fractionated external beam radiotherapy resulted in stabilization of the mass with eventual progression after 14 mo, samarium-153-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid was administered systemically, and the cat showed immediate, whole-body improvement in mobility. Concurrent intestinal and respiratory disease was evaluated and managed. Samarium-153-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid administration was repeated approximately every 6 mo for three treatments until the cat succumbed to thromboembolic disease attributed to previously diagnosed cardiac disease. Radiation therapy administered using either external beam or bone-seeking radioisotopes can be effective at palliating clinical signs associated with the skeletal abnormalities that accompany this disease.