Rosai-Dorfman Disease: A Rare Presentation as a Papular Eruption

Summary: Rosai-Dorfman disease is a proliferative histiocytic disorder typically involving cervical lymph nodes, with or without constitutional symptoms. Extranodal involvement occurs in nearly half of patients. Pure cutaneous Rosai Dorfman disease (CRDD) is a rarer entity that most frequently presents with clusters of erythematous, violaceous, and hyperpigmented papules and nodules coalescing into plaques or large exophytic masses. Here we report a case of a 69-year-old man who presented with a 2-month history of multiple asymptomatic pink smooth edematous papules on the chest, back, and thighs. The patient’s eruption had been preceded by severe bilateral bacterial conjunctivitis. The patient denied any associated weight loss or other constitutional symptoms. No evidence of lymphadenopathy or extracutaneous disease was detected. Several skin biopsy specimens were similar, revealing a nodular infiltrate of S100 protein-positive large histiocytes associated with a prominent inflammatory infiltrate composed of lymphocytes and plasma cells, some binucleated and trinucleated, with admixed eosinophils. Emperipolesis was observed. These findings were consistent with RDD. Clinicians should be aware of this atypical presentation, adding RDD to the differential diagnosis of papular eruptions.