Superficial granulomatous pyoderma.

Introduction. Superficial granulomatous pyoderma is a rare variant of pyoderma gangrenosum, which is often diagnosed at a late stage because of misleading clinical-histopathological features. We report a new case of this rare disease. Case report. A 67 year-old man presented with inflammatory lesions that had become ulcerated over the Past 4 months despite prolonged antibiotic therapy. The histopathological aspect was initially suggestive of palisading granuloma annulare and subsequently a necrotizing granuloma compatible with a mycobacteriosis. The various supplementary examinations eliminated the possibility of an infectious or systemic disease. The lesions became painful and ulcerated. A second biopsy showed a neutrophilic dermatosis with dermal necrosis and a granuloma leading to the diagnosis of superficial granulomatous pyoderma. The lesions healed after 3 months of systemic corticosteroids at the dose of 1 mg/kg/day. Discussion. The clinical features of superficial granulomatous pyoderma are similar to those of classical pyoderma gangrenosum. However, its histological profile is more superficial and is associated with dermal granulomas. The latter are unusual in neutrophilic dermatosis and would suggest an infectious disease. This explains the frequent diagnostic errors, with inappropriate anti-infectious treatments and notably unnecessary surgical exeresis.