Pyoderma Gangrenosum

Pyoderma Gangrenosum Posted By:
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A patient presents to your clinic with a painful, rapidly expanding ulcer on a lower extremity. If pyoderma gangrenosum (PG) isn't on your differential, it should be. Pyoderma gangrenosum is a rare, reactive neutrophilic dermatosis that, if undiagnosed, can be life-altering and potentially limb-threatening.

Often initially mistaken for infection, PG is considered a diagnosis of exclusion. Clinically, the patient may present with a history of a pustule or pustular plaque rapidly expanding into a painful ulceration, sometimes preceded by trauma. The pathophysiology of PG is not entirely understood, but is thought to be a complex interplay between neutrophil dysfunction and aberrant triggering of inflammatory mediators that arise in a genetically susceptible individual.

Classic ulcerative PG is often characterized as a pustular plaque that rapidly evolves into an ulceration with active, violaceous, and gun-metal grey undermined borders that often heals with cribriform scarring. In many cases minor trauma can trigger the development of PG, illustrating the concept of pathergy, which can be seen in up to 30% of PG cases. Active ulcerations are often extremely painful and purulent, which frequently contributes to misdiagnosis as a primary infectious process. In extreme cases, misdiagnosis as infection has led to unnecessary surgical debridement and even limb amputation. Other clinical variants of PG include pustular, peristomal, bullous, and vegetative.

While some cases are idiopathic, 50% of PG cases are associated with an underlying condition. Conditions associated with PG include inflammatory bowel disease, paraproteinemias, hematologic malignancies, rheumatoid arthritis, and solid organ malignancies. As such, a thorough review of systems should be performed, and additional workup should be conducted based on abnormalities identified. Prompt referral to dermatology is critical. A biopsy of the active border of the ulcer should be performed and sent for hematoxylin and eosin (H&E) staining, as well as tissue culture sent for bacterial, fungal, and atypical mycobacterial pathogens. Classic histopathology for PG reveals a neutrophilic infiltrate in the dermis. Classic PG is typically steroid responsive, but given the complications associated with long-term systemic corticosteroid use, steroid-sparing agents such as cyclosporine (CsA), dapsone, methotrexate, mycophenolic acid, and tumor necrosis factor (TNF)-inhibitors are used for long term disease management.

Although rare, it is important for every clinician to consider PG in the differential when working up a patient with a rapidly expanding ulceration, as a delay in diagnosis can be devastating. Understanding of the associated conditions seen with PG is critical in providing the patient with the thorough evaluation they require.

References
  • Alavi A, French LE, Davis MD, et al. Pyoderma gangrenosum: An update on pathophysiology, diagnosis and treatment. Am J Clin Derm. 2017;18:355-372.
  • Bobonich MA, Nolen ME. Dermatology for Advanced Practice Clinicians. Philadelphia, PA. Wolters Kluwer; 2015.
  • Saffie MG, Shroff A. A case of pyoderma gangrenosum misdiagnosed as necrotizing infection: A potential diagnostic catastrophe. Case Rep Inf Dis. 2018:8907542.

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Filed under: Dermatology

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