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952 Superficial Necrolytic Dermatitis

Superficial Necrolytic Dermatitis Client Education
Sheet
VetBooks.ir Etiology and Pathophysiology

BASIC INFORMATION
• The skin lesions are due to degeneration of network throughout the liver, resulting
in a honeycomb or Swiss cheese pattern.
Definition keratinocytes, and it is thought that deficien- Occasionally, hepatic metastases are
Progressively debilitating skin disease associated cies (essential fatty acids, zinc, biotin, and detected.
with severe internal disease process particularly hypoaminoacidemia) resulting ○ Ultrasonographic detection of pancreatic
from metabolic abnormalities caused by liver and extrapancreatic glucagonomas can be
Synonyms dysfunction or hyperglucagonemia play a difficult.
Hepatocutaneous syndrome, glucagonoma major role in the pathogenesis. • Histopathologic exam of tissue (± immuno-
syndrome, metabolic epidermal necrosis, • Hypoaminoacidemia in affected dogs promi- histochemical staining)
necrolytic migratory erythema nently involves amino acids associated with ○ Skin biopsy: epidermis has a French flag
the urea cycle and synthesis of glutathione appearance (i.e., red-white-blue layers):
Epidemiology and collagen. The most consistent and severe ■ Upper layer (stratum corneum):
SPECIES, AGE, SEX abnormalities involve glutamine, proline, parakeratotic hyperkeratosis staining
• Uncommon in dogs, rare in cats cysteine, and hydroxyproline. red (eosinophilic)
• Middle-aged to geriatric patients • Dysfunction of specific amino acid trans- ■ Middle layer (stratum spinosum):
porters and wasting of amino acids essential intracellular edema, vacuolation, and
GENETICS, BREED PREDISPOSITION for collagen synthesis are evidenced by necrosis of the keratinocytes staining
• Possible heritable component in shih marked lysinuria and prolinuria in affected white (pallor)
tzus dogs. ■ Deep layer (stratum basale): hyperplasia
• Several hepatopathies have possible genetic staining blue (basophilic)
component (p. 450) DIAGNOSIS • Ultrasound-guided hepatic biopsy: first
perform platelet count, arterial blood pres-
RISK FACTORS Diagnostic Overview sure, and coagulation panel to assess bleeding
• Administration of phenobarbital Diagnosis is usually based on clinicopathologic, risk; hepatic neoplasia or idiopathic vacuolar
• Ingestion of mycotoxin ultrasonographic, and histopathologic findings. hepatopathy
• Other assays
ASSOCIATED DISORDERS Differential Diagnosis ○ Fasting and postprandial bile acid values
• Most cases are associated with hepatopathy. • Autoimmune/immune-mediated derma- are frequently elevated (nonspecific).
• Few cases are associated with functional topathy: pemphigus foliaceus, drug-induced ○ Complete plasma amino acids
pancreatic alpha-cell (glucagon-secreting) pemphigus, systemic lupus erythematosus, (hypoaminoacidemia supportive of
tumor. paraneoplastic pemphigus, cutaneous vascu- diagnosis of superficial necrolytic
• Diabetes mellitus reported to occur in litis, erythema multiforme, toxic epidermal dermatitis [SND]) testing is available
25%-40% of dogs with hepatic form necrolysis at Amino Acid Analysis Laboratory
• Other associated conditions in dogs: hepatic • Infectious dermatopathy: bacterial (pyo- Service, University of California, Davis.
cirrhosis, idiopathic vacuolar hepatopathy, derma), fungal (dermatophytosis, Malassezia Generalized hypoaminoacidemia, with
extrapancreatic glucagonoma (liver, spleen, dermatitis), protozoal (leishmaniasis) numerous amino acid concentrations <
adrenal glands, and mesenteric lymph nodes), • Parasitic dermatopathy: demodicosis 50% of mean reference values. Contact
copper storage disease, hyperglucagonemia, • Nutritional dermatopathy: zinc-responsive laboratory for sample handling and cost
and intestinal disease dermatosis (https://www.vetmed.ucdavis.edu/labs/
• Associated diseases in cats: pancreatic • Neoplastic dermatopathy: epitheliotropic amino-acid-laboratory).
carcinoma, hepatopathies, and thymic lymphoma ○ Urinalysis: marked lysinuria and
amyloidosis • Idiopathic: nasodigital hyperkeratosis prolinuria
○ Pancreatic tumors may not be readily
Clinical Presentation Initial Database visible with abdominal ultrasonography;
HISTORY, CHIEF COMPLAINT • Deep skin scrapings (typically negative, therefore, measurement of plasma gluca-
Owners usually observe footpad lesions first although secondary demodicosis may occur), gon is also recommended.
because dermatologic changes may precede cytologic evaluation of the skin (patients
onset of clinical signs of internal disease. Leth- often have a bacterial or Malassezia over- TREATMENT
argy, anorexia, weight loss, lameness, reluctance growth) ± dermatophyte culture (typically
to walk/signs of pedal pain, and pruritus are negative) (p. 1091) Treatment Overview
frequently reported. Other chief complaints • CBC (nonregenerative anemia and leuko- Treatment consists of a three-pronged approach:
may include polyuria and polydipsia. cytosis are possible), serum biochemistry supportive therapy for dermatologic manifesta-
profile (elevated alkaline phosphatase, alanine tions, management of internal disease process
PHYSICAL EXAM FINDINGS aminotransferase, serum glucose and (which may require hospitalization), and
Dermatologic lesions are characterized by fructosamine levels; hypoalbuminemia; surgical removal of neoplasm when possible.
thickening, fissuring, and crusting of footpads decreased blood urea nitrogen), and urinalysis
and interdigital erythema. Crusts, erosions, (glucosuria if diabetic) Acute General Treatment
and ulcers can affect pinnae, mucocutane- • Pain management
ous junctions (oral cavity, eyes, anus, and Advanced or Confirmatory Testing • Treat secondary bacterial and fungal
genitalia), elbows and other pressure points, • Abdominal ultrasonography infections with appropriate therapy (avoid
and ventral abdominal and inguinal regions. ○ Changes in hepatic parenchyma are systemic azole antifungal therapy because of
Regional lymphadenopathy and hyperthermia highly characteristic: hypoechoic potential hepatotoxicosis).
are possible. nodules with a hyperechoic trabecular • Gentle shampoo therapy

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