Immunoreactivity to dermal vessels in a patient with pyoderma gandrenosum


Introduction: Pyoderma gangrenosum (PG) represents a lesion with an elusive etiology associated with Crohn’s and/or arthritic diseases. A genuine associated vasculitis has not been proven; however, dilation of the dermal blood vessels the presence of neutrophilic and/or lymphocytic infiltrates in selected biopsies suggests that vessels are likely play a role in the pathogenesis of PG.

Materials and Methods: A patient presented with a necrotic pustule or furuncle, evolving into a large necrotic ulcer with violaceous borders and surrounding erythema. A skin biopsy for hematoxylin and eosin (H&E) review and immunohistochemistry (IHC) stains was obtained. A second biopsy for direct immunofluorescence (DIF) was also taken.

Results: H&E review demonstrated an ulcerated epidermis; within the ulcer base were numerous neutrophils, lymphocytes, histiocytes and fibrin. No vasculitis was present. DIF revealed strong deposits of FITC conjugated fibrinogen around superficial and the deep dermal vessels. FITC conjugated Complement/C1q and albumin conjugated were also seen between dermal extracellular matrix fibers. IHC showed that the dermal vessels (venules, arterioles and lymphatics) displayed dilation, and a loss of normal endothelial markers including von Willebrand factor and D2-40/podoplanin.

Conclusions: Our case of PG shows that there seems to be an alteration of several skin structures, including dermal vessels. An alteration of the vascular fibrin-fibrinogen balance was also detected, causing some autoreactivity to fibrinogen and an immune response involving neutrophils and T lymphocytes. Our findings suggest that the etiology of PG is more complex than previously thought.

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