Pyoderma gangrenosum or necrotizing fasciitis? A diagnostic conundrum. Case report and literature review

Necrotizing fasciitis (NF) is a life-threatening, rare soft tissue infection characterized by rapidly spreading necrosis of the fascia and subcutaneous tissue, muscle, and overlying skin. Once suspected, immediate and extensive surgical debridement of necrotic tissues and appropriate systemic antibiotic coverage are necessary. On the contrary, pyoderma gangrenosum (PG) is an auto-inflammatory condition of the skin that has been associated with multiple factors including inflammatory bowel disease, arthritis, and myelodysplastic disorders. It is a non-infectious process requiring non-surgical management. Both conditions are rare in the pediatric population, and may present with significant ulceration and tissue necrosis. Lack of diagnostic clinical, histopathologic, and laboratory features make identification of these entities challenging. We present a case of pyoderma gangrenosum, initially diagnosed as cellulitis and necrotizing fasciitis, to highlight the diagnostic challenges involved in differentiating these disease entities and clinical implications of misdiagnosis or delayed diagnosis.