The patient was a normothermic, adult, castrated male horse with a six-month history of progressive lameness and pain upon palpation of the scapulae and bones of the neck and spine. Widespread, sharply delineated, radiolucent bone lesions were identified on radiographs of the vertebrae, scapulae, ribs, mandibles, and pelvis. Diffuse bronchointerstitial lung pattern was noted on thoracic radiographs. Complete blood cell count, serum chemistry, serum electrophoresis were unremarkable with the exception of mild microcytic normochromic anemia. The primary differential included metastatic neoplasia.
What is the most likely diagnosis?
A. Fibrous osteodystrophy
B. Silicosis-associated osteoporosis
C. Multiple myeloma
D. Fibrous dysplasia
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We will reveal the answer in next month’s issue!
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Answer to last issue’s Case of the Month… A. Succinate dehydrogenase Last month’s images showed a paraganglioma, a rare tumor arising from the paraganglia that form the sympathetic or parasympathetic tissue and the adrenal medulla. In people who have germline mutations of genes encoding one of several components of the succinate dehydrogenase enzyme (such as SDHB, SDHC, SDHD, or SDH5), the incidence of paragangliomas is 30 percent by the age of 30 (1). SDH gene mutations can be found in in 10 percent of sporadic paragangliomas, which typically occur as multiple tumors in younger patients. SDHB mutations are the most ominous; they are associated with malignancy of tumors in about 50 percent of cases. The absence of immunohistochemical staining with the antibody to the SDHB protein is considered sufficient evidence of an underlying SDH germline mutation.
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