Granulomatosis and Polyangiitis Presenting as Superficial Granulomatous Pyoderma

Author(s): Sophia Zhang, Ellen Roh, Timothy Patton

Superficial granulomatous pyoderma (SGP) is one of four subtypes of pyoderma gangrenosum (PG), an uncommon neutrophilic dermatosis, that presents as superficial, indolent ulcerative nodules or plaques that arise independently from an associated underlying disease [1]. Granulomatosis and polyangiitis (GPA) is a systemic, cytoplasmic ANCA (cANCA) positive vasculitis of small and medium vessels classically presenting with a triad of vascular, pulmonary, and renal complications [2]. We report a case of a limited variant of GPA presenting as SGP in a 57- year-old male with multiple nonhealing, painful ulcers on the upper extremities, torso, and neck with histologic features of superficial ulcers with predominantly plasma cell infiltrate consistent with atypical SGP. Over the following year, violaceous ulcers appeared, and a larger wedge biopsy demonstrated sinus tract formation with underlying plasmocytosis with histiocytes and giant cells, neutrophilic inflammation, and focal granuloma formation without vasculitis. The patient developed pulmonary symptoms and fever in the setting of markedly elevated cANCA. A chest CT revealed a lung nodule with fine needle aspiration (FNA) demonstrating acute and granulomatous inflammation but no organisms. Based on compatible clinical and histological findings, the diagnosis of GPA presenting as SGP was established. This case of a variant of GPA initially limited to the integument and mistaken for SGP characterizes the clinical and histopathological presentations of two rare diseases and supports the notion that GPA should be included in the differential diagnosis for SGP even before systemic symptoms and elevated cANCA arise to ensure early diagnosis and treatment.