Drug eruptions include a full spectrum of diseases from simple drug eruptions to more severe erythema multiforme to the most severe which is toxic epidermal necrolysis. Drug eruptions like systemic lupus can be a great imitator and mimic many diseases, especially autoimmune diseases. The most common drugs that are implicated in canine drug eruptions include sulfonamides and cephalosporins. Drug eruptions are often targetoid lesions (bulls-eye) but can also be papular, vesicular and crusting.
     • Diagnosis of drug eruptions are made with thorough history. Histopathology can be quite variable. In many cases, they appear like a classic pemphigus case. Many cases have single cell keratinocyte necrosis to even full thickness epidermal necrosis as seen in TEN.
     • Treatment for drug eruptions include drug removal and supportive therapies such as IV fluid therapy and Silvadene Creams. Antibiotics may or may not help. Corticosteroid therapy is not recommended. Cyclosporine may be beneficial in erythema multiforme.

Toxic epidermal necrolysis (TEN) is the rarest of the drug eruptions but the most lethal. In the widespread necrosis of the skin, patients often have pyrexia, anorexia, lethargy and pain.
     • Toxic epidermal necrolysis (TEN) should always be given with a poor prognosis.
     • Treatment is to remove inciting drug/cause if possible and supportive care.

Necrolytic migratory erythema (Hepatic Cutaneous syndrome) is a syndrome that is usually seen in older animals. Hepatopathy, pancreatic or liver neoplasia are usually associated with NME. Diabetes Mellitus is often seen, especially later in the course of NME. Secondary staph and/or malassezia infections are often present. Necrolytic migratory erythema patients exhibit erythema, erosions, ulcerations and crusting often in the mucocutaneous syndromes with footpad hyperkeratosis and ulcerations often leading to lameness.
     • Diagnosing NME: Dermatopathology is diagnostic with often talked of the red, white and blue pattern seen by the pathologist. Ultrasound of the liver will often show a swiss cheese type of appearance.
     • Treatment for necrolytic migratory erythema should be based on amino acid intravenous supplementation. Amino acids are given weekly to biweekly usually through a central line to improve skin lesions. Concurrent antibacterial and antifungal drugs are used as needed. Contrary to logic, sometimes glucocorticoid therapy will be helpful in NME cases.

Demodicosis can be a lethal disease due to extreme expense or extreme frustration of the owner. Demodicosis is seen in 2 populations of canine patients. The younger genetic cases of demodicosis and older populations secondary to an immune-suppressing disease. Sometimes demodicosis can be secondary to chronic allergic diseases due to long term steroid use and even immune dysfunction from the chronic allergic disease.
     • Diagnosing demodicosis is done through skin scrapings, hair plucks and occasionally dermatopathology.
     • Treatment for demodicosis involves long-term antibiotic therapy for the secondary pyoderma, treating the underlying systemic diseases if possible.
     o Mitaban (amitraz) dips weekly to biweekly usually done in hospitals due to possible owner issues handling the dip.
     o Ivermectin 300-600mcg/kg daily orally. Ivermectin should not be used in herding breeds unless MDR1 genotyping has been shown that the patients will tolerate it. This is typically done through Washington State University's laboratory.
     o Doramectin? Promerus?

Cutaneous Neoplasias

1. Mass cell tumors
2. Squamous cell carcinoma
3. Mucoid Cutaneous melanoma
4. T-Cell lymphomas

Cutaneous T-Cell lymphoma is a proliferation of T-lymphocytes that have an epidermal affinity often leading to micro abscesses in the epidermis called Pautrier's micro abscesses. Many forms of T-cell are seen in the dog including a generalized erythema scaling, mucocutaneous depigmentations with erosions, crusting plaques, nodules to frank tumors.
     • Diagnosing neoplastic skin diseases involve dermatopathology.
     • Treatment for cutaneous T-cell lymphoma is often difficult with a variable prognosis and usually best treated through a medical oncologist. CCNU appears to be the treatment of choice but Prednisone, Safflower oil, Accutane and other vitamin A analogs have also been used to treat cutaneous T-cell lymphoma.

Paraneoplastic alopecia is a recently described syndrome in older cats that have a rather classic shiny skin with exfoliated alopecia. These cats often have weight loss and/or anorexia and ultrsonographic examination will usually reveal pancreatic carcinoma.
     • Treatment options are poor for this syndrome and usually involve supportive care but a grave prognosis should be given to the owners.