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Superficial Necrolytic Dermatitis
Mitchell D. Song, DVM, DACVD

VETMED Specialty Referral and 24‐Hour Emergency Care Veterinary Hospital, Phoenix, AZ, USA

Etiology/Pathophysiology not enough reported cases to enable accurate determina-
tion of breed or sex predilection, though one paper
Superficial necrolytic dermatitis (SND), also known as reported a predilection towards Shih tzus.
hepatocutaneous syndrome and metabolic epidermal
necrosis, is an uncommon, generally fatal, crusting and
scaling skin disease, which is similar to necrolytic migra- Clinical Signs
tory erythema in humans. It has been described in dogs,
cats, and black rhinoceroses. For the purposes of this Skin lesions are mostly associated with those areas on the
chapter, the remaining discussion will be confined to the body where trauma naturally occurs, including the foot-
disease in dogs. pads, muzzle, and mucocutaneous junctions (periocular,
Superficial necrolytic dermatitis is an external mani- perioral, anal and genital regions). It is not uncommon for
festation of an internal disease, most commonly advanced lesions to also develop on the elbows, hocks, and margins
hepatopathy, but it has also been associated with gluca- of the pinnae. The development of cutaneous lesions is
gonoma, ingestion of mycotoxins or long‐term pheno- often the reason for owners to seek veterinary advice. The
barbital and phenytoin treatments. There is a recent case footpads typically become thickened, crusted, and fis-
report describing SND associated with an insulin‐ and sured which often leads to pain and lameness (Figure 169.1).
glucagon‐producing pancreatic carcinoma. Diabetes The elbows, hocks, and prepuce may be alopecic, erosive
mellitus can be a complication of this disease. to ulcerated, erythematous, crusty, and scaly (Figure 169.2).
The exact etiopathogenesis of SND is currently unknown. Secondary bacterial and fungal (often yeast) infections
Several studies investigating the serum amino acid profile of occur frequently and aggravate the cutaneous lesions
dogs with SND have found profound hypoaminoacidemia, associated with SND.
indicating that this may participate in the development of In cases where there is severe liver disease, dogs may
skin lesions because amino acids are necessary to maintain have jaundice of the sclera and/or mucous membranes.
cellular integrity in the epidermis. In one study, glutamic In cases associated with diabetes, dogs may be polydipsic
acid, phenylalanine, tryptophan, and ornithine were not sig- and polyuric.
nificantly different but all other amino acids were 60% or less There are many laboratory abnormalities associated
than the mean reference values for normal dogs. In 72% with SND, which may vary according to the individ-
of the dogs studied, either glutamine or arginine was the ual case and underlying disease. Those that have
most diminished plasma amino acid. Deficiencies in been reported include mild to severe normocytic,
cutaneous essential fatty acids, zinc, and biotin have also normochromic, nonregenerative anemia, microcytosis,
been suggested to play a role in skin lesion development. hyperglycemia, glucosuria, and possibly ketonuria if the
patient has developed diabetes mellitus. Urine amino
acids including lysine, proline and 1-methylhistidine
Signalment are increased. Increases in liver enzymes, hypoalbu-
minemia, decreases in creatinine and phosphorus, and
Superficial necrolytic dermatitis is a disease of older increases in cholesterol and triglycerides have also been
dogs, with an average age of 10 years. Currently, there are reported. It should be noted that there is no clinical

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical