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.


VETERINARY MEDICINE



Vital Stats
Our differential diagnoses for the dermatologic lesions included systemic lupus erythematosus (SLE), pemphigus complex, demodicosis with furunculosis and secondary bacterial pyoderma, folliculitis or furunculosis secondary to a staphylococcal dermatitis, dermatophytosis, erythema multiforme, toxic epidermal necrolysis, and canine juvenile cellulitis. We considered a drug eruption less likely because there was no known history of drug therapy before the lesions appeared. Our differential diagnoses for the acute-onset right tarsal joint effusion included an infectious arthritis, an immune-mediated arthritis (erosive or nonerosive), and degenerative joint disease secondary to unknown trauma. Our differential diagnoses for the multiple subcutaneous nodular lesions included infection (e.g. bacterial, fungal, parasitic, protozoal), sterile inflammatory disorders (e.g. nodular panniculitis, sterile granuloma or pyogranuloma syndrome, reactive systemic histiocytosis, xanthomas, canine juvenile cellulitis), and, less likely, neoplasia. We attributed the dog's tachypnea to pain and the fever, and we attributed the nasal planum depigmentation to irritation from the serosanguineous discharge from the skin lesions.

Initial diagnostic tests

The dog was hospitalized, and we performed a complete blood count (CBC), serum chemistry profile, and urinalysis. The abnormal results of the CBC (Table 1) revealed leukocytosis with a regenerative left shift, 1+ toxic change, and monocytosis. These changes were consistent with chronic active inflammation. We interpreted a nonregenerative, macrocytic, hyperchromic anemia as an anemia of chronic disease with artifactual increases in mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration from in vitro hemolysis.


Abnormal Laboratory Test Results
The abnormal results of the serum chemistry profile (Table 1) revealed mild hyperphosphatemia, hyperglycemia, hypercholesterolemia, and a mild increase in alkaline phosphatase activity. We attributed the elevated phosphorus concentration and alkaline phosphatase activity to physiologic increases associated with growth. We attributed the hyperglycemia to stress and the moderate hypercholesterolemia to a postprandial increase.

The results of urinalysis (sample collected by cystocentesis) revealed a slightly low urine specific gravity (1.020), hematuria (80 to 100 RBC/hpf) and trace proteinuria. The hematuria was iatrogenic, and the results of a urine protein:creatinine ratio to quantify the proteinuria and rule out concurrent glomerulonephritis were normal (0.43, reference range < 1). Serum was also submitted for an antinuclear antibody titer.

Treatment and further tests

On Day 1, we initiated intravenous fluids (Plasmalyte 148 [Baxter] with 16 mEq/L potassium chloride added), morphine sulfate (0.2 mg/kg subcutaneously q.i.d.), and cephalexin (22 mg/kg orally b.i.d.) as prophylaxis for secondary bacterial skin infections.


4. A photomicrograph of the dog's skin showing multifocal to coalescing pyogranulomatous inflammation surrounding several follicles (hematoxylin-eosin; bar = 500 m).
On Day 2, the dog remained febrile, and inguinal lymph node enlargement and additional truncal subcutaneous masses had developed. The dog was anesthetized and prepared for arthrocentesis of multiple joints, including the right tarsal joint. We performed arthrocentesis of the right stifle, right carpus, and both tarsi. The synovial fluid was grossly normal from all joints except the right tarsus. The synovial fluid from the right tarsus was serosanguineous and had decreased viscosity. This joint had been aspirated by the referring veterinarian five days before, so we suspected secondary iatrogenic blood contamination.

While the dog was anesthetized, we obtained multiple representative full-thickness 4-mm punch biopsy samples of abnormal tissue from the periocular region, muzzle, chin, inner pinnae, prepuce, and truncal skin for histologic examination. The enlarged lymph nodes and truncal subcutaneous masses were also aspirated for cytologic evaluation. Grossly, the aspirate of the right submandibular lymph node appeared abnormal, consisting of serosanguineous fluid. The referring veterinarian had previously aspirated this lymph node and noted an increase in plasma cells and lymphoblasts.


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Source: VETERINARY MEDICINE,
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