Upon physical examination, Penny appeared moderately lethargic and showed multiple subcutaneous-dermal nodules over her trunk and over the right side of her thoracic inlet and shoulder, abdomen and groin (see Figs 1, 2). There were also a few hemorrhagic bullae (one is 1.5 inches in diameter, 1 is 1/2 inch diameter) on the ventral abdomen. One nodule was approximately located in the submandibular lymph node area. Peripheral lymph nodes were moderately enlarged. The rest of the physical examination was within normal limits (body weight 4,3 kg; HR 180; RR 24; temperature 101,8 F).
CBC and chemistry showed only minor changes: WBC=17.800/μL; Segs=12.240/μL; Monocytes=1.800/μL; albumin=2.700 g/dL. The rest of values were all WNL. Fine needle aspirates of two of the nodules are similar and revealed a pyogranulomatous exudate, without detection of infectious agents (Fig. 3). A lymph node FNA revealed only a reactive hyperplasia.
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Our initial differential diagnosis included:
- Inflammatory nodules with infectious origin: bacterial (e.g. Nocardia spp, Mycobacteria spp); fungal (e.g. Cryptococcus spp, Sporothrix schenkii) or protozoal (Leishmania spp)
- Sterile nodular panniculitis
- Juvenile cellulitis (puppy strangles)
Three 6 mm punch biopsies were obtained from the skin nodules biopsy under sedation and local anesthesia. Biopsies were halved. Half of each sample was fixed in formalin was sent to the Pathology Lab for histopathologic analysis. Two halves were sent to the microbiology lab for fungal and bacterial culture and the remaining half was kept frozen for future analysis (PCR or other molecular techniques).
Bacterial and fungal cultures were both negatives. The histological diagnosis was “Multifocal to coalescing, chronic, marked, pyogranulomatous panniculitis and dermatitis, consistent with nodular panniculitis “. All special stains for infectious agents were negative and the pathologist added as a comment in his report “findings are compatible with sterile nodular panniculitis”. Therefore, a final diagnosis of sterile nodular panniculitis was made.
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Treatment and Outcome
Penny was put on a tapering course of oral prednisone (5mg /q 24k for one week; 2.5 mg/q 24h for a second week and 2.5 mf/ q 48 h for a third week) and on 25 mg of cyclosporine once daily, PO. The cyclosporine was given with food and the capsules kept in the freezer, to reduce the probability of GI adverse events. Three weeks later, when the prednisone was withdrawn, the nodules had reduced markedly their size. Blood work was all WNL. Three weeks later the nodules had completely disappear (Figs 4, 5). The cyclosporine was administered for two more weeks daily and then 4 for more weeks at the dose of 25mg/q 24h and stopped.
Contreary CL, Outerbridge CA, Affolter VK et al. Canine sterile nodular panniculitis: a retrospective study of 39 dogs. Vet Dermatol 2015 26: 451-458. http://www.ncbi.nlm.nih.gov/pubmed/26283563