A challenging case: A febrile dog with a swollen tarsus and multiple skin lesions - Veterinary Medicine
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A challenging case: A febrile dog with a swollen tarsus and multiple skin lesions
The condition that these clinicians suspect in this Labrador is considered a late-onset manifestation, even though the dog is only 9 months old.


5. A photomicrograph of the dog's skin showing perifollicular pyogranulomatous inflammation surrounding and effacing sebaceous and sweat glands (hematoxylin-eosin; bar = 100 m).
We also obtained multiple deep skin scrapings of the lesions and normal areas of skin while the dog was anesthetized, and microscopic examination failed to reveal ectodermal parasites, making demodicosis unlikely. Cytologic examination of an impression smear from an intact pustule showed mixed inflammation with nondegenerate neutrophils and macrophages. Cytologic examination of the impression smears of the draining lesions on the face and prepuce also showed mixed inflammation with nondegenerate neutrophils and macrophages. No infectious agents were seen in any of the samples examined cytologically.

The findings from the cytologic examination of aspirates from the prescapular and submandibular lymph nodes and the truncal masses were consistent with pyogranulomatous inflammation. The submandibular lymph nodes also contained epithelioid macrophages. The findings from the cytologic examination of the inguinal lymph node aspirates were consistent with reactive lymphoid hyperplasia. No infectious agents were seen.

Cytologic analysis of the joint fluid revealed that the right carpus was normal; the right tarsus showed neutrophilic inflammation, the left tarsus showed mononuclear inflammation, and the right stifle showed mixed mononuclear and neutrophilic inflammation. No infectious agents were seen in any of the joint fluid samples. No growth occurred on an aerobic bacterial culture of the right tarsal joint fluid, making septic arthritis less likely. The results of aerobic bacterial cultures of fluid from the right submandibular lymph node and fluid from one of the skin pustules were negative, making staphylococcal dermatitis less likely. No infectious agents were seen after Gram's and acid-fast staining in any of the samples submitted for culture.

6. A photomicrograph of the dog's skin showing inflammation surrounding and infiltrating hair follicles, leading to rupture of the follicles (hematoxylin-eosin; bar = 100 m).
On Day 2, we initiated an immunosuppressive dosage of prednisone (1 mg/kg orally b.i.d.) because we suspected an immune-mediated disorder. On Day 3, the dog developed mucopurulent ocular discharge. The results of a complete ophthalmic examination were normal except for bilateral conjunctivitis, likely secondary to irritation from periocular skin disease. We prescribed a bacitracin/neomycin/polymyxin B/hydrocortisone ophthalmic ointment (topically to both eyes t.i.d.). On Day 4, the dog was clinically much brighter and no longer febrile, so we discontinued intravenous fluids. We discontinued the morphine on Day 5. For the first two days in the hospital, the dog was anorectic and showed no interest in food, but by Day 6, the dog was eating well.

Histologic results and diagnosis

The results of the histologic examination of the skin biopsy samples revealed inflammatory nodular dermal infiltrates that centered around hair follicles and often partially or completely effaced the associated sebaceous and sweat glands (Figures 4 & 5). In some areas, the follicles had ruptured (Figure 6). The inflammatory infiltrates were composed mainly of neutrophils and epithelioid macrophages with smaller numbers of plasma cells and lymphocytes (Figures 7 & 8).

7. A photomicrograph of the dog's skin at higher magnification showing some well-delineated granuloma-like lesions. (hematoxylin-eosin; bar = 50 m).
The histopathologic diagnosis was nodular pyogranulomatous dermatitis with folliculitis and furunculosis. Unfortunately, none of the skin biopsy samples included the subcutis, so the presence of nodular sterile panniculitis could not be conclusively confirmed. But the cytologic findings from these subcutaneous nodules were supportive of this presumptive diagnosis. No evidence of an interface dermatitis or any other epidermal abnormalities characteristic of SLE was present. In addition, the results of the ANA titer were negative, making SLE less likely; however, some dogs with SLE have negative ANA titer results, so the titer results alone cannot be used to conclusively rule out SLE. We ruled out pemphigus complex because no evidence of subcorneal or intragranular pustules or suprabasilar vesicles with acantholysis was present. Likewise, the histopathologic lesions were not consistent with erythema multiforme or toxic epidermal necrolysis, which typically result in epidermal lesions. A primary staphylococcal folliculitis or furunculosis seemed unlikely because of the systemic nature of the disease, the lack of cocci bacteria in any of the samples, and the negative bacterial culture results from the skin. The histologic findings and the clinical signs (cutaneous and systemic) most closely fit with a diagnosis of late-onset canine juvenile cellulitis.


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