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Abstract

In a patient with numerous comorbidities, nonspecific clinical findings can lead to a wide differential diagnosis. We present a case of a 62-year-old male with a two-month history of asymptomatic hyperpigmented papulonodules on the elbows. The patient had a medical history of MPO-ANCA vasculitis with associated pauci-immune glomerulonephritis and cystic disease of the lungs. His history also included long-standing IgG lambda MGUS and mucoepidermoid carcinoma status post parotidectomy. The clinical differential diagnosis included a perforating disorder, calcinosis cutis in the setting of renal disease, metastasis of mucoepidermoid carcinoma, possible lymphoma related to MGUS, and gout. Skin biopsy revealed superficial and deep multifocal nodular dermal infiltrates composed of sheets of histiocytes surrounding broad zones of necrobiotic stroma and basophilic debris; within these zones were collections of neutrophils. These findings were consistent with palisaded neutrophilic and granulomatous dermatosis (PNGD), which typically presents in patients with underlying lupus erythematosus or rheumatoid arthritis.  It also occurs with underlying hematologic malignancies, solid tumors, drug reactions and infections. Our patient's history of MPO-ANCA vasculitis, mucoepidermoid carcinoma, and underlying MGUS were possible causes for his clinical and histologic findings. Treatment of PNGD may involve intralesional or systemic corticosteroids; other systemic immunosuppressive medications such as hydroxychloroquine may be beneficial and can be helpful in managing patients’ underlying rheumatologic disease.  This case highlights the nonspecific clinical appearance of PNGD, our limited knowledge of the underlying mechanism which results in the clinical lesions and highlights the utility of a biopsy and deciphering potential links to multiple ongoing systemic inflammatory diseases.