Degenerative Skin Disorder (Necrolytic Dermatitis) in Dogs

Superficial necrolytic dermatitis (SND) is a disease in which dogs develop skin lesions. Lesions are found most commonly on the pads of the feet, face or belly. The lesions are caused by a metabolic imbalance that isn’t fully understood. Dogs have low levels of amino acids and zinc in their blood, and in some cases, increased blood glucagon (a hormone that normally works to counter insulin). A similar condition is found in humans, most frequently caused by a glucagonoma, a glucagon-secreting tumor in the pancreas. Like humans, dogs may develop superficial necrolytic dermatitis because of a pancreas tumor, but in dogs, this condition is more typically associated with liver disease. Liver failure is frequently from a glycogen-type vacuolar hepatopathy. This is a condition in which the liver cells take on extra glycogen (starch storage molecules). Liver disease can develop secondary to the skin lesions and in the later stages lesions or nodes may form on the liver also. Diabetes mellitus is also frequently found in dogs with this condition, but the exact relationship isn’t fully understood. Drug and mycotoxin poisoning can contribute to the problem also. Amino acid supplements and a high protein diet can sometimes be effective, but dogs with this condition don’t have a high rate of survival.

Dogs can develop necrotic skin lesions as the result of a complex metabolic imbalance. The lesions are often a sign of liver disease or a tumor in the pancreas. Veterinarians call this superficial necrolytic dermatitis. It is a rare condition with limited options for treatment.

Skin symptoms are usually the first sign, but systemic illness may develop as the disease progresses. Take your dog to see a veterinarian if you notice any of the following signs.

• Red patches of skin (erythema)
• Ulcerated skin
• Crusted lesions
• Pus
• Hardened skin (hyperkeratosis)
• Cracked foot pads
• Loss of toenails
• Hair loss (alopecia)
• Secondary fungal or bacterial infection
• Weight loss
• Lethargy
• Excessive drinking
• Frequent urination

Types

SND is rare in dogs and the types haven’t been well defined. Veterinarians could use any of the following names to define a similar condition.

• Metabolic dermatitis 
• Necrolytic migratory erythema
• Glucagonoma syndrome
• Hepatocutaneous syndrome

SND in dogs is not fully understood and most cases are essentially idiopathic. It is most commonly associated with these conditions.

• Hepatopathy (liver disease such as vacuolar hepatopathy, idiopathic hepatocellular collapse)
• Phenobarbital use (anticonvulsant drugs)
• Mycotoxin exposure
• Glycogen producing tumor in the pancreas, sometimes with metastasis to the liver
• Diabetes
• Cushing’s disease
• More common in older dogs

The veterinarian will perform a complete physical examination. Skin lesions can be visually observed, but a biopsy will be also taken to analyze the cells under a microscope. Blood tests will usually show hyperglycemia (high blood sugar) and low amino acid levels. Liver failure may also be apparent. Elevated ALP (alkaline phosphatase) is the most consistent sign of liver disease, but other liver enzymes may also be abnormal. If there is no sign of liver failure, and the dog has high levels blood levels of glucagon, the veterinarian will suspect a glucagonoma tumor rather than hepatopathy. 

X-rays will be taken to check for tumors on the pancreas as well as in the stomach and intestine. Occasionally a gastric tumor can also cause SND. With vacuolar hepatopathy the liver will often be increased in size and an ultrasound will show what is called a “Swiss cheese pattern” with cells abnormally enlarged from glycogen content. A liver biopsy may be necessary to evaluate the cells at a microscopic level.

The most effective treatment for dogs with SND is injection an intravenous amino acid concentration. This is given over a period of 8-12 hours. There is some risk with this treatment since dogs can develop a metabolic disturbance called hyperammonemia. The veterinarian will monitor your dog and this problem should resolve itself within a day after treatment. Four treatments may be tried at 1 week intervals or until skin lesions show improvement. 

A high protein diet designed for dogs with liver dysfunction is recommended, as well as oral amino acid supplements. Fatty acid and zinc supplements can also help support your dog’s metabolism. Secondary infection is common, so antibiotics and antifungal medication may be prescribed. The lesions should be cleaned frequently with a topical antiseptic to reduce the risk of infection. Corticosteroids are not recommended. If a glucagon-secreting tumor is found on the pancreas or elsewhere, the veterinarian may recommend surgery to remove it. If the cancer is successfully removed, your dog’s symptoms may improve significantly. If your dog is taking a phenobarbital medication, the veterinarian will discontinue it, if possible. Removal of mycotoxin exposure can also lead to improvement in skin lesions.

Medication may be prescribed for concurrent diabetes mellitus. Diabetes found with SND is typically insulin resistant, so it can be difficult to treat. This may be a result of increased glucagon in the blood which could counteract insulin, but, unlike humans, not all dogs have high glucagon levels. The exact relationship between the lesions and systemic disease isn’t fully understood.

Careful management of the condition will be needed to prolong your dog’s life. Your dog will need to follow a strict diet and take regular supplements and medication. The lesions will need to be cleaned frequently. Most dogs with SND have a guarded outlook, especially if the cause is undetermined. If a mycotoxin or drug toxicity is the source of the problem, it may be resolved by reducing exposure to the toxin. Cancerous tumors can sometimes be removed successfully, but most forms of cancer come back eventually and your dog will still have a reduced life expectancy. The veterinarian will discuss the likelihood of successful treatment upon diagnosis.