On the basis of the above history and physical examination, the differential diagnoses for the lameness included soft tissue injury, orthopedic injury, and septic arthritis. Differential diagnoses for the skin problem included ear mites and otitis externa. A blood sample was collected for a complete blood cell (CBC) count (QBC Vet Autoread IDEXX Laoratories, Westbrook, Maine, USA). There was mild normochromic anemia (hematocrit 28 L/L; reference range, 29 to 33.8 L/L), moderate eosinophilia (3.0 × 10⁹/L; reference range, 0 to 8 × 10⁹/L), and high normal number of white blood cells (18.6 × 10⁹/L; reference range, 11.3 to 20.1 × 10⁹/L) and neutrophils (11.4 × 10⁹/L; reference range, 5.6 to 11.4 × 10⁹/L) (1). Cytologic examination of an ear swab was negative for ear mites. Anemia and eosinophilia suggested a hookworm infestation; however, no eggs were observed on a fecal flotation. Results from a serum biochemical analysis (VetTest; IDEXX) were unremarkable.

The puppy was treated with amoxicillin/clavulanic acid (Clavamox Drops; Pfizer, London, Ontario), 12.5 mg/kg bodyweight (BW), PO, ql2h for 7 d, and ketoprofen (Anafen Tablets; Merial, Baie d'Urfé, Quebec), 0.5 mg/kg BW, PO, q24h for 4 d. On day 2, the owner reported that the condition of the puppy had remained unchanged, other than for the development of small “pimples” on the lower lip. The puppy was returned to the clinic on day 3 exhibiting severe lethargy. However, it was still eating and drinking normally, and there had been no vomiting or diarrhea. Pyrexia had resolved (38.3°C) and the puppy appeared well hydrated. Numerous pustules were present on the muzzle, the pinnae, around the eyes, and on prepuce. The puppy was unwilling to either walk or stand even when lifted. Shoulders, elbows, and carpi were bilaterally painful on flexion and extension. Differential diagnoses were expanded to include juvenile cellulitis (puppy strangles) and, less likely, deep staphylococcal pyoderma with secondary septicemia. The owner was advised to monitor the puppy at home closely in hopes of seeing a response to the antibiotic and anti-inflammatory drug treatments.

By day 4, the puppy's condition had improved only slightly. A marked pustular and exudative dermatitis of the face and purulent otitis externa were present. Some lesions had fistulated and crusted. The CBC count and serum biochemical analysis were repeated, and a urinalysis was performed. Results of the CBC count were similar to those previously obtained. All parameters on the serum biochemical and urinalysis were within reference ranges. A sample for culture and sensitivity testing was collected from a pustule on the lower lip and submitted to Vita-Tech Veterinary Laboratory Services, Toronto, Ontario. The antibiotic was switched to cefadroxil (Cefa-Drops; Ayerst, Guelph, Ontario), 22 mg/kg BW, PO, q12h for 14 d, and the puppy was prescribed meloxicam (Metacam oral suspension; Boehringer, Burlington, Ontario) 0.1 mg/kg BW, PO, q24h for 7 d.

As juvenile cellulitis had become the primary differential diagnosis, diagnostic tests were conducted to make a definitive diagnosis. On day 5, submandibular lymph nodes were slightly enlarged and prescapular lymph nodes were markedly enlarged. Under general anesthesia (Isoflurane, Bemeda-MTC, Cambridge, Ontario), induced and maintained with a mask, 2 excisional mandibular skin biopsies were performed to include pustules. Two biopsies were also performed on the left prescapular lymph node by using a 3.5-mm biopsy punch. Samples were collected into 10% buffered formalin and submitted for histopathologic examination (Histo Vet Surgical Pathology, Guelph, Ontario). Arthrocentesis was performed on both carpi to obtain samples of synovial fluid, which were smeared on glass slides. Slides were air dried and also submitted for cytologic examination (Histo Vet).

By day 7, the clinical condition of the puppy began to improve markedly. The puppy became more active and the pustules had begun to resolve. Histopathologic examination of the skin biopsies revealed pyogranulomatous perifolliculitis, most likely due to juvenile cellulitis. In the skin and subcutaneous tissue, neutrophils were very well preserved and no bacteria could be seen. Lymph node biopsies did not contain lymph node tissue, probably because of edema around the lymph nodes. Stained joint smears revealed mild serous effusion with increased synoviocytes, compatible with mild degenerative joint disease, joint trauma, or both. Culture and sensitivity testing of the lip pustule revealed no growth after 72 h incubation. On the basis of the diagnosis of juvenile cellulitis, the puppy was treated on day 8 with prednisone (Predsone-5; Vetcom, Upton, Quebec), 15 mg, P0, q24h for 14 d. By day 10, the lameness had resolved and the muzzle and otic lesions had decreased in size and number. Prednisone treatment was tapered over 3 d, beginning on day 15, as the skin lesions had been reduced to small areas of alopecia and the puppy was clinically normal.

Juvenile cellulitis is an uncommon granulomatous and pustular disorder of the face, pinnae, and submandibular lymph nodes, most commonly seen in puppies less than 4 mo of age (2,3). Although, in this case, lameness and depression were noted first, the initial clinical finding is often an acutely swollen face, with particular involvement of the eyelids, lips, and muzzle. These signs are often accompanied by submandibular lymphadenopathy. Within 24 to 48 h, papules and pustules develop around the lips, muzzle, chin, bridge of the nose, and in the periocular area (2). Occasionally, lesions may also appear on the feet, abdomen, thorax, vulva, prepuce, or anus (4). Lesions typically fistulate, drain, and crust. Marked pustular otitis externa is common, with the pinnae frequently being thickened and edematous. Affected skin is often painful but not pruritic (2). Approximately 50% of affected puppies are lethargic and depressed (2,3), as in this case. Pyrexia, anorexia, and sterile suppurative arthritis, manifesting as joint pain, are inconsistent findings (2,4). Leukocytosis with neutrophilia, and normocytic, normochromic anemia may also be seen (5).

Although the onset was atypical in this case, signs quickly progressed to match the classic clinical picture of juvenile cellulitis. Juvenile cellulitis may be diagnosed primarily on a clinical basis, as in this case (5). However, definitive diagnosis requires cytologic and histopathologic evaluations. Cytologic examination of papulopustular lesions of juvenile cellulitis reveals pyogranulomatous inflammation with no microorganisms, as in this case, and carefully performed cultures are negative. Biopsies of early lesions reveal multiple discrete or confluent granulomas and pyogranulomas consisting of clusters of large epithelioid macrophages with variably sized cores of neutrophils. Cytological analysis of joint fluid often reveals sterile suppurative arthritis (2), which did not occur in this case.

The cause of juvenile cellulitis is unknown. Cytologic examination of aspirates of affected lymph nodes, pustules, abscesses, and joint fluid rarely reveal bacteria, and culture results of intact lesion are always negative for bacterial growth, suggesting a nonbacterial etiology. The condition responds dramatically to corticosteroids, suggesting an immune dysfunction (5). Large doses of glucocorticoids are the treatment of choice. Early and aggressive therapy is indicated, otherwise scarring may be severe (2). If cytological or clinical evidence of secondary bacterial infection exists, bactericidal antibiotics, such as cephalexin, cefadroxil, and amoxicillin clavulanate, should be prescribed (2,6). Although the clinical condition of the puppy in this case had begun to improve before initiation of glucocorticoid therapy, the response was more rapid once corticosteroids were added to the treatment regime.