18 Metabolic epidermal necrosis
Metabolic epidermal necrosis (MEN), also known as superficial necrolytic dermatitis, necrolytic migratory erythema and hepatocutaneous syndrome, is a cutaneous reaction pattern associated with systemic disease. In dogs it has been associated with hepatic disease (cirrhosis, neoplasia and hepatitis), glucagon-secreting pancreatic tumours, with antiepileptic drugs such as phenytoin and phenobarbitone, and with mycotoxins. In humans, it is mostly associated with glucagon-secreting pancreatic tumours, although it may also be found in patients with liver cirrhosis or celiac disease. Recently, MEN has been subdivided into those cases associated with hepatic dysfunction and without a pancreatic tumour (MEN-HS), cases associated with a glucagon-secreting pancreatic syndrome (MEN-GS), and cases where there are raised liver enzymes, but the presence of a pancreatic tumour is not conclusively ruled out (MEN-ND).
Duration of the condition at presentation is usually a few days to a few weeks. Most cases present with progressive skin lesions consisting of erythema, crusting and scaling over pressure areas and, frequently, lameness. These symptoms are poorly responsive to any treatment although there may be temporary improvement with antimicrobial therapy. There may be a history suggestive of systemic involvement with lethargy and perhaps anorexia. There may be gastrointestinal signs associated with hepatic dysfunction and many dogs develop concurrent diabetes mellitus resulting in polyuria and polydipsia. Pruritus is uncommon, but owners may report that the dog is foot licking.
General examination may reveal hepatic enlargement and abdominal pain, or may be unremarkable. A cutaneous examination usually reveals symmetrical facial and pedal distribution of lesions. Other areas of friction are commonly affected, and in some cases lesions on the ventral abdomen and other mucocutaneous sites may develop as the condition advances. Lesions usually consist of thick adherent crusts, erythema, exudation, erosions, ulceration and fissuring. The footpads are almost always involved, with lesions ranging from mild to severe hyperkeratosis, erosions and fissuring. Lesions on the ventral abdomen resemble target lesions, with a central area of hyperpigmentation surrounded by crusts and scale which can progressively coalesce to involve large areas. Often, secondary bacterial and Malassezia colonization is also reported.