Immune-mediated dermatitis and myositis is a 8-year-old Siberian Husky mix
Contributed by Dr. Adam Mordecai
Veterinary Specialty Center
Buffalo Grove, IL

Clinical History
An 8-year-old (40.8 kg) male neutered Siberian Husky/Border Collie mix dog presented to the Dermatology Department at the Veterinary Specialty Center for evaluation of a several month history of superficial pyoderma.  Over the 3-4 weeks prior to presentation slowly progressive lethargy, weakness and voice change developed. The skin lesions were characterized by serous crusting and patchy alopecia (see pictures below). Skin scrapings were negative and Tzanck preparations  revealed moderate cocci and low  numbers of degenerative neutrophils.  The serum creatine kinase activity was elevated  (9856 IU/L; reference <200).  A low dose dexamethasone suppression test showed suppression of cortisol at 4 hours with escape at 8 hours. An abdominal ultrasound was performed and revealed mild hyperechoic hepatomegaly and gallbladder sludge. The adrenals were normal. Additionally there was mild sublumbar lymph node enlargement. The dog was transferred to the Internal Medicine Department for further evaluation.

Physical and Neurological Exam
The body temperature was mildly elevated at103.3 and other vitals were normal. With the exception of the skin lesions and shaking in the pelvic limbs, physical and neurological examinations were normal.

Diagnostic Testing
Thoracic radiographs – Normal
Testing for infectious diseases included antibody titers for Neospora , Toxoplasma, and Ehrlichia canis by IFA -All negative
Skin biopsies collected with 6 mm biopsy punch – Eosinophilic and lymphoplasmacytic dermatitis  and perivasculitis
Muscle biopsies – Biopsies were collected from the vastus lateralis  and triceps muscles.  Lymphocytic myositis (see below left, H&E stain) and mild necrotizing myopathy were evident in both muscles.

Treatment and Outcome:
Treatment was initiated with doxycycline 300 mg PO twice daily while waiting for results of the skin and muscle biopsies.  Following receipt of biopsy results, prednisone 40 mg twice daily and azathioprine 50 mg orally once daily were added for treatment of immune-mediated dermatitis and myositis. Clinical signs of weakness, lethargy, skin abnormalities  and voice change all improved  within one week following initiation of immune suppressant therapy. The serum CK activity was normal at the one month recheck. Prednisone was decreased to 40 mg once daily followed by a further reduction to 20 mg once daily. Azathioprine was reduced to 50 mg every other day. One month following the last taper, clinical signs began to reoccur  and prednisone was increased to 40 mg once daily for 3 days, then to 30 mg  daily. Periodic adjustments of prednisone are needed to maintain clinical remission. 



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