Nonresponsive Skin Lesions in a Siberian Husky

On examination, Trooper was bright, alert, and responsive. All peripheral lymph nodes were normal. Periocular regions were alopecic with mild to moderate crusting (Figure). The pinnae were moderately erythematous on the concave surface with mild adherent scaling. The scrotum was severely erythematous. All paw pads were crusted. The remainder of the examination was unremarkable.

Evaluation of an impression smear of the periocular region revealed numerous cocci with streaming neutrophils. A deep skin scrape was negative for ectoparasites. Skin biopsies were discussed with Trooper’s owner; however, superficial pyoderma was initially treated prior to biopsy to ensure accurate results. Bacterial culture and susceptibility testing was performed on the lesions to guide therapy.

Four days after initial presentation, culture results revealed methicillin-resistant Staphylococcus schleiferi (Table). Treatment with chloramphenicol (40 mg/kg every 8 hours) was initiated. In addition, the owner was instructed to bathe Trooper weekly using a 3% chlorhexidine/phytosphingosine shampoo. Due to the location of the periocular lesions, topical therapy did not seem appropriate as the sole means of eliminating pyoderma.

Infection had improved significantly 2 weeks after initial presentation, and Trooper was returned to the clinic for punch biopsies (6 mm) of the affected areas, performed while he was under sedation. The specimens were submitted for histopathology, which confirmed zinc-responsive dermatosis (see Histopathology Results of Punch Biopsies Indicating Marked Parakeratotic Hyperkeratosis).

Chloramphenicol therapy was continued for 4 weeks, including 1 week after resolution of clinical signs of infection and cytologic cure. Supplementation with zinc methionine (elemental zinc, 3 mg/kg once daily [dose can be split and given every 12 hours]) was initiated (see Treatment at a Glance).^1-3

Trooper was rechecked 1 month after zinc therapy was initiated; lesions showed some improvement, and evaluation of an impression smear confirmed the absence of bacteria. Low-dose methylprednisolone (initial dose, 0.7 mg/kg once daily) was initiated and tapered over 1 month. In many cases, low-dose corticosteroids can be beneficial for treatment of dogs that do not respond to zinc alone,⁴ as corticosteroids are known to increase zinc absorption from the GI tract.

Trooper was presented 6 weeks later for a recheck examination. He had not received methylprednisolone for 2 weeks, and all lesions were resolved. Zinc methionine supplementation was continued, and Trooper was free of lesions. Lifelong zinc supplementation is typically needed. Long-term prognosis is favorable as long as zinc supplementation is maintained.

Zinc-responsive dermatosis syndrome I is a condition that occurs primarily in Alaskan malamutes, Siberian huskies, and other arctic breeds and may be associated with defective intestinal absorption of zinc.^1,2,5

Syndrome II occurs in dogs fed a zinc-deficient diet.^1,2,6 The author has anecdotally seen an increase in the number of syndrome II cases that may be a result of an increase in dogs being fed home-prepared and alternative diets. Lesions are typically located at mucocutaneous junctions and paw pads and appear as areas of erythema with scaling, crusts, and hyperkeratosis.

Zinc-responsive dermatosis should be on the differential diagnosis list for crusted skin disease in any northern- or arctic-breed dog (see Take-Home Messages). Diagnosis is made through history and biopsy. Serum or hair levels of zinc may be low in affected patients; however, proper analysis can be difficult due to a variety of factors, so biopsy is the recommended diagnostic test if zinc-responsive dermatosis is suspected.⁷