Presentation and history Nina, an 11-year-old female spayed miniature pinscher, was presented to us for an examination relating to a left-sided facial wound from what was suspected to be a draining tract from a carnassial tooth abscess. Medical history was unremarkable, except for a history of chronic ear infections. Nina was seen two months earlier at her primary care hospital for a dental procedure to extract endodontically diseased teeth 208 and 209. Within days postoperatively, Nina became painful and swollen on the left side of her face, with enlargement of the left mandibular lymph node and left-sided epiphora. Oral amoxicillin/clavulanate was started, which helped decrease the initial postoperative swelling. Nina was presented one month later with pain and a draining tract of the skin ventral to her left eye, and was started on clindamycin and meloxicam. Anesthetized exam one month later at another primary care facility revealed grossly purulent draining tract and firm soft tissue in the left infraorbital region. No retained root tips were identified on dental radiographs. Five additional teeth were extracted. Aerobic culture of the discharge from the draining tract showed no bacterial growth. At recheck examination at the primary care facility two weeks later, the ulcerated area on the facial skin was larger and encroaching on the left ventral eyelid. Triple antibiotic ophthalmic ointment was started in the left eye. A recommendation was made to pursue consultation with a specialist. When she was presented to Sarah Bronko, DVM, and myself, Nina was receiving meloxicam once a day, gabapentin every eight to 12 hours, and clindamycin twice daily. Nina’s appetite had not been affected throughout and was eating soft food readily. Physical exam findings included severe left facial ulceration, which was exudative with crusty discharge on skin and surrounding fur. The wound was present from midline dorsal muzzle, extending caudally ventral to the left eye, and was beginning to destroy the lower eyelid at the medial canthus (Figure 1A). The ulceration extended ventrally to within 1 cm of the left caudal lip margin. The left buccal mucosa was missing in the area of the left upper lip vestibule. The left eye appeared enophthalmic. The patient’s temperature was slightly elevated at 102.9 F. A grade II/VI systolic heart murmur was auscultated on the left side of the chest. The left mandibular lymph node was moderately enlarged. There was an open, ulcerated orocutaneous fistula in the left maxillary mucosa in the region of previously extracted 207-208. Teeth 207 through 210 were missing due to previous extractions. Figures 1A and 1B. A) Nina, an 11-year-old miniature pinscher, presented with nonhealing wound on the left face. B) Dental radiograph of left maxilla. Tooth 205 has a wide canal suggesting a nonvital tooth. Photos courtesy Dr. John R. Lewis Diagnoses Differential diagnoses included bacterial infection, neoplasia, immune-mediated disease, fungal infection, and osteomyelitis. Diagnostics performed included dental radiographs of the left maxilla, which revealed no evidence of retained roots or endodontic disease, except for nonvital tooth 205, which was far from the ulcerated area (Figure 1B). A cone-beam CT scan showed an ill-defined, severe soft tissue swelling of the left maxilla with heterogeneous enhancement. The adjacent nasal and maxillary bones were moderately lytic with associated irregular and amorphous new bone proliferation. The left medial retropharyngeal lymph node was mildly enlarged. The tympanic bullae, external ear canals, and paranasal sinuses were normal. No abnormalities were noted at the level of the salivary glands and thyroid glands. Biopsies of affected skin, gingiva, and mucosa were obtained and submitted for histopathology, fungal tissue culture, bacterial tissue culture (aerobic and anaerobic), and left mandibular lymph node aspirate/cytology. Nonvital tooth 205 was extracted via closed technique. Gingival edges were sutured closed with a simple interrupted pattern with 5/0 poliglicaprone 25. No attempt to close the cutaneous defect was made. Clinical suspicion I had seen one or two prior cases very similar to Nina’s, both of which responded amazingly well to corticosteroids, when antibiotics and NSAIDs did not help. As we waited for culture and histopathology results, Nina’s owner was instructed to discontinue meloxicam in anticipation of possibly starting prednisolone. Treating a case like this with steroids can be scary. What if soft tissue ulceration was being caused by a resistant infection? What if the changes seen in the bone were more than just reactive? What if this was due to some weird fungal disease that steroids might make worse? These scenarios were all discussed with Nina’s owners, but we felt we had to act quickly to preserve her lower eyelid, which seemed to be melting away. After a washout period of four days without NSAIDs, prednisolone was begun at an immunosuppressive dose (approximately 1.5 mg/kg/day), and when she returned for her two-week postoperative recheck, Nina was showing signs of significant improvement. There was a marked reduction in left facial swelling. The area of ulcerated skin was smaller. Enophthalmos of the left eye appeared to be resolved. Mandibular lymph nodes palpate smaller in size than previously. Figure 2. At the two-week recheck, Nina shows signs of improvement on chloramphenicol and an immunosuppressive dose of prednisolone. Her eye is no longer enophthalmic, and the area of ulcerated skin is reduced. Photo courtesy Dr. John R. Lewis Around that time, test results became available. Histopathology showed chronic ulcerative and suppurative dermatitis and stomatitis, of which the inciting cause was not evident. Neoplastic populations and evidence of autoimmune disease were not seen, and infectious bacterial or fungal organisms were not seen with either routine or special stains. The bacterial culture and sensitivity grew methicillin-resistant Staph. pseudointermedius, which was resistant to everything except amikacin, gentamycin, and chloramphenicol. Fungal culture did not grow anything. Left mandibular lymph node cytology showed a reactive node. The side effects and risks of chloramphenicol were discussed, and after a phone consultation with a veterinary dermatologist, Nina was placed on oral chloramphenicol at 40 mg/kg q8h for one month, along with topical mupirocin, thin film to the site twice daily. Nina continued to improve, even after discontinuation of the chloramphenicol. Her prednisolone dose was slowly tapered over many months. Nina is now 18 months beyond her initial presentation, and the skin in the area of the ulcerated defect has filled in with a combination of haired skin and hairless scar tissue (Figures 3A and 3B). Even a portion of the missing lower eyelid regenerated while on steroids. Nina has been off steroids entirely for one month with no signs of recurrence thus far. Figure 3A and 3B. Nina 17 months after starting prednisolone for treatment of suspected immune-mediated skin disease. Hairless scar tissue has filled in the ulcerated area, and a missing portion of the lower eyelid has regrown. Photos courtesy Dr. John R. Lewis We may never know what caused Nina’s skin and mucosal problems, but there are a few possibilities that come to mind within the realm of immune-mediated/autoimmune disease. Erythema multiforme affects the haired skin, mucosa, and gingiva.1 Other immune-mediated or autoimmune diseases can affect both skin and mucosa.1 However, Nina’s clinical presentation and histopathology fit best with a rare disease called pyoderma gangrenosum. This is a rare immune-mediated neutrophilic ulcerative dermatitis that has been reported in only a handful of veterinary patients.2,3 Pyoderma gangrenosum has been documented to occur at sites of prior trauma,4 so it may be that an initial draining tract from endodontic disease was an initiating cause in Nina’s case. Pyoderma gangrenosum may also be seen as an initial manifestation of systemic disease.4 Keep this rare disease in mind next time you see a patient with a “melting” face. John R. Lewis, VMD, DAVDC, Fellow, AVDC OMFS, practices at Veterinary Dentistry Specialists and teaches at Silo Academy Education Center, both in Chadds Ford, Pa. References Dosenberry C, Arzi B, Palm C, Vapniarsky N, Soltero-Rivera M. An update on oral manifestations of systemic disorders in dogs and cats. Front Vet Sci. 2025 Jan 6;11:1511971. doi: 10.3389/fvets.2024.1511971. PMID: 39834923; PMCID: PMC11743369. Simpson DL, Burton GG, Hambrook LE. Canine pyoderma gangrenosum: a case series of two dogs. Vet Dermatol. 2013 Oct;24(5):552-e132. doi: 10.1111/vde.12065. Epub 2013 Aug 9. PMID: 23931071. Declercq J. An atypical case of pyoderma gangrenosum in a dog. @inproceedings {Declercq2018AAA, title={A An atypical case of pyoderma gangrenosum in a dog Een atypisch geval van pyoderma gangrenosum bij een hond}, author={Jana Declercq}, year={2018}, url={https://api.semanticscholar.org/CorpusID:102340346} Cruz M, Zelaya De Leon NI, Duran LG, Petasny M, Grassi NA, Montenegro Fernández MG, Zorzano Osinalde P, Otamendi M, Espinoza FE. Pioderma gangrenoso como manifestación inicial de enfermedad sistémica [Pyoderma gangrenosum as an initial manifestation of systemic disease]. Medicina (B Aires). 2025;85(5):1132-1137. Spanish. PMID: 41109295.
