Veterinary Medicine - March 2008 - (Page 152)

A challenging case PEER-REVIEWED In dogs, the lesions are most common on the footpads, elbows, hocks, face, ventral abdomen, and perineum. glucagonomas in dogs, skin lesions were also a primary complaint.5,8 In dogs, the skin lesions are most commonly identi ed on the footpads, elbows, hocks, face, ventral abdomen, and perineum. The terms super cial necrolytic dermatitis, metabolic epidermal necrosis, diabetic dermatosis, hepatocutaneous syndrome, and necrolytic migratory erythema have been used to describe the skin lesions in dogs.5,6,8-11,14 Unlike necrolytic migratory erythema in people, super cial necrolytic dermatitis in dogs appears to occur most commonly with a hepatopathy (hepatocutaneous syndrome) and less commonly with a glucagon-secreting tumor.15 tions. The high glucagon concentrations promote amino acid mobilization in tissues because of the need for substrate in prolonged gluconeogenesis.3 Glucagon’s subsequent activation of the urea cycle enzymes carbamoyl-phosphate synthase and argininosuccinate synthase promotes the catabolism of amino acids. These pathways of protein degradation are hypothesized to cause hypoaminoacidemia, which causes cellular necrosis in the epidermis by depleting epidermal proteins.2 Liver disease along with fatty acid and zinc de ciencies may also contribute to the pathogenesis of the skin lesions in some cases.2 A similar pathogenesis may exist for super cial necrolytic dermatitis in dogs. Serum amino acid concentrations were determined in three of the eight reported cases, and 20 of 24, 13 of 18, and four of ve amino acids tested were found to be decreased.5 Amino acid concentrations were not determined in this case. Histologic features. In people, the skin lesions include parakeratotic hyperkeratosis and moderate epidermal hyperplasia associated with intracellular edema of the upper portion of the stratum spinosum. The lesions create distinctive layers: intensely eosinophilic, keratinous cellular debris super cially; pale-staining edematous keratinocytes in a middle layer; and a deep zone of basophilic hyperplastic basal cells. Similar histologic changes have been identi ed in dogs with glucagon-secreting neoplasms or hepatic disease (hepatocutaneous syndrome). Because the characteristic lesions are not seen in every punch biopsy sample from an affected patient, three to ve biopsies are recommended. Pathogenesis. In people, the pathogenesis of the skin disease is thought to be an indirect result of chronically elevated plasma glucagon concentra- Diabetes mellitus and nonspeciﬁc clinical signs Hyperglycemia or glucose intolerance in association with diabetes mellitus has been reported in people with glucagon syndrome and in some dogs with glucagonomas.2,5,15 Diabetes mellitus is hypothesized to be due to glucagon’s diabetogenic actions.2 However, the development of diabetes mellitus most likely depends on the glucagon:insulin ratio, the relative proportion of other hyperglycemic hormones, and the preexisting genetic tendency toward glucose intolerance.2 In this case report, the patient had no evidence of concurrent diabetes mellitus. 152 March 2008 VETERINARY MEDICINE

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Veterinary Medicine - March 2008 Contents Toxicology Brief Idea Exchange A Challenging Case An Update on Diagnosing and Treating Primary Lung Tumors CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - March 2008

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