Superficial Necrolytic Dermatitis

Chapter 118

Superficial Necrolytic Dermatitis

Superficial necrolytic dermatitis (SND) was initially reported in dogs as “diabetic dermatopathy” because of the association of the disorder with diabetes mellitus (Walton et al, 1986). There is a similar skin disorder in humans: necrolytic migratory erythema. Necrolytic migratory erythema is usually associated with a malignant neuroendocrine tumor called a glucagonoma. Most cases of SND in dogs are associated with liver disease, are termed the hepatocutaneous syndrome (HS) form of SND, and are not associated with a glucagonoma. However, there have been a few reported cases of the glucagonoma syndrome (GS) form of SND in dogs. A small number of cases of SND have been associated with medications (phenobarbital, primidone) and mycotoxin ingestion. The number of reported cases of SND in cats is relatively low.

Clinical Findings in Dogs

The disease is more common in middle-aged or older dogs. Primary complaints of SND in dogs include soreness of the dog’s paws and lethargy or anorexia. The most useful clinical findings in dogs are abnormalities of the paws, including crusts, erythema, and oozing. Usually all paw pads exhibit varying degrees of hyperkeratosis with subsequent crusting and fissuring of the pads. Lesions including erythema, erosions or ulcerations, serous to purulent discharge, crusts, and hyperkeratotic plaques may occur in other sites such as perioral, perianal, perivulvar, preputial, and scrotal skin. Differential diagnoses of the lesions of SND include zinc-responsive dermatosis, pemphigus foliaceus, erythema multiforme, epidermolysis bullosa acquisita, and bullous pemphigoid. Impression cytologic analysis of SND lesions is usually helpful in revealing the presence of secondary infections, which are commonly associated with this disease. Complete blood count (CBC) may reveal mild nonregenerative anemia and leukocytosis.

Dogs with SND (HS) have elevated levels of liver enzymes (serum alkaline phosphatase, alanine transaminase) and increased bile acids; some have hyperglycemia with or without other features of diabetes mellitus. Abdominal ultrasonography is useful to check for the presence of the hyperechoic and hypoechoic pattern within the liver often seen in dogs with SND (HS). This pattern is sometimes described as having a “Swiss cheese” or “honeycomb” appearance.

The absence of abnormal results on the serum chemistry panel makes it more likely that the dog may have the GS form of SND. Thus, in cases of SND without evidence of liver disease, thought needs to be given to the possibility of SND (GS). Abdominal ultrasonography may not be able to detect small pancreatic tumors. Magnetic resonance imaging might be able to distinguish small tumors, although contrast enhancement may be necessary. It is recommended that the owners of dogs suspected of having SND (GS) submit a sample of the dog’s plasma for glucagon measurement and that the results be compared with published information on canine plasma glucagon. High levels of plasma glucagon support the possibility that a glucagon-secreting tumor is present. Unfortunately, assays for canine plasma glucagon usually are not available, and the sample must be submitted to a human endocrinology laboratory that measures human plasma glucagon level. It may be beneficial to consult a specialist in internal medicine or endocrinology.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Superficial Necrolytic Dermatitis

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