Cutaneous Rosai-Dorfman disease: a challenging diagnosis.

Rosai-Dorfman disease is a rare benign histiocytic proliferative disease of unknown cause that, in exceptional cases, presents with lesions confined to the skin. Clinically variable types of lesions such as papules, nodules and plaques have been reported. We present a case of a 27-year-old woman with a 1-year history of erythematous papular and nodular lesions on the malar and right axillary regions, previously misdiagnosed as acne. She reported no fever, malaise or weight loss, while physical examination and laboratory workup were normal. Bacteriological and mycobacteriological cultures were negative. Histopathological findings showed dense infiltration of inflammatory cells involving the entire dermis, consisting of large macrophages with emperipolesis, S100 and CD68 positive, neutrophils, eosinophils, lymphocytes and plasma cells. The patient was treated with oral prednisolone without improvement. Dapsone was subsequently initiated with favourable clinical response. The present article aimed to emphasise the clinical and histological differential diagnosis and share the treatment experience.