Rosai-Dorfman Disease Case Report.

Introduction: Rosai-Dorfman disease (RDD) is a rare histiocytic disorder that is characterized by the accumulation of histiocytes in various tissues, most commonly the lymph nodes. Cutaneous RDD is a rare presentation, accounting for less than 10% of all RDD cases.

Case presentation: An 18-year-old female presented for the first time with a dome-like lesion over an indurated plaque. Both lesions were biopsied, and findings suggested RDD. The patient was referred to an oncologist with a subsequent positron emission tomography scan showing hypermetabolic subcutaneous uptake on bilateral thighs and bilateral lumbar lesions, likely corresponding to the patient's biopsy-proven histiocytosis in addition to a diffuse increased tracer uptake in the thoracic aorta and atria.

Conclusion: A high degree of suspicion is necessary when dermatologists notice two different morphologies present in proximity to rule out a single pathological process. This case is unique because of the rarity of the condition as well as the clinical presentation of two different morphologies of an indurated plaque and a dome-like lesion on the same area of the body.