A 3-year-old, spayed female Bernese Mountain Dog was presented with pustules and crusts, which were developed at 10 days after an operation for pyometra, on the ventral abdomen. Blood tests, serum TT4 level, bacterial and fungal cultures of the skin lesions, and X-ray and ultrasonography of the chest and abdomen revealed no abnormalities except for leucocytosis, high level of alkaline phosphatase and low TT4. Histopathological findings of the skin lesions showed neutrophilic infiltration in the epidermis and superficial dermis. Administration of oral prednisolone, azathioprine, cyclosporine, and minocycline or amoxicillin/clavulanic acid as antimicrobials were not effective, and follicular oriented pustules were spread to the whole body. The bacterial culture of the pustule yields negative, and the histopathological findings of the pustules revealed subcorneal pustule containing numerous neutrophilis and a few acantholytic cells. Direct and indirect immunofluorescence tests, which were performed at the first and second biopsy, showed no deposition of IgG or IgA on the surface of keratinocytes or basement membrane zone. When antibiotics were changed to fosfomycin, the pustules on the whole body were rapidly dissapeared. From the clinical course and examination results, it was suspected that the present dog was diagnosed with sterile pustulosis associated with alternative immune function caused by bacterial infection to the other organs.

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The diagnostic value of Total T4 (TT4) levels was reconsidered in dogs with skin disorders. TT4 (CLEIA, Mitsubishi Chemical Medience Corporation, Animal Laboratory Center) was evaluated in 161 dogs requiring examination for hypothyroidism and in 7 clinically healthy dogs. In dogs with hypothyroidism, TT4 was 0.2 ± 0.6 μg/dl, which was apparently lower than the normal range (0.5-2.8 μg/dl), was less than the lowest mean TT4, 1.3 μg/dl, in dogs with various skin diseases besides hypothyroidism. Based on these findings, it was suggested that TT4 levels were consistently low in dogs with hypothyroidism, and useful as a screening test if mean TT4 in dogs without hypothyroidism was used for the reference value.

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