Paws to Patients: Canine Pyoderma Gangrenosum as a Reflective Model of Human Pyoderma Gangrenosum

Human pyoderma gangrenosum (hPG) is a rare, non-infectious neutrophilic dermatosis characterized by painful, necrotic ulcers with violaceous borders. Research on hPG is limited by minimal existing animal models, the sole being a pharmacologically induced murine model. Few cases of canine pyoderma gangrenosum (cPG) have been published, and dogs are genetically closer to humans than are mice, making them a potentially valuable model of hPG. We aimed to characterize all published cPG cases and compare their presentation to that of hPG. A Google Scholar, PubMed, and Embase search of "canine AND pyoderma gangrenosum" was conducted in August 2024, with seven case reports, two case series, and two veterinarian-sourced cases ultimately reviewed. Of the 31 analyzed cPG cases, 30 presented with skin ulcers at multiple sites, the most common being the trunk (64.5%), paws (41.9%), and limbs (32.3%), mirroring the typical localization of hPG on the lower extremities, back, and abdomen. The average age of cPG presentation was 7.8 +/- 3.7 years (range: 0.25-14.5 years). Dogs reflected hPG comorbidities, with 16.1% presenting with gastrointestinal pathologies, 6.5% with arthritis, and 6.5% with hematologic disorders. Dogs were responsive to medications frequently employed in hPG-prednisone/prednisolone (80.6%) as initial therapy, and cyclosporine (77.4%) as maintenance therapy. Overall, cPG resembles hPG in affected anatomic sites, comorbidities, and therapeutic response. It offers a representative, spontaneously occurring hPG animal model alternative to the existing murine model. Future studies are necessary to reproduce cPG to further investigate disease pathophysiology.