Primary Cutaneous Rosai-Dorfman Disease With Typical Immunophenotype But Lacking Emperipolesis: A Case Report

Background: Cutaneous Rosai–Dorfman disease (CRDD) is a rare extranodal histiocytosis that can mimic other dermatoses, particularly when hallmark emperipolesis is absent. Case Presentation: A 50-year-old man presented with 5 months of intensely pruritic lesions affecting the palms, soles, flexures, and limbs. Skin biopsy revealed a nodular infiltrate of foamy histiocytes extending into the subcutis. Immunohistochemistry showed S100⁺, CD68⁺, CD1a⁻, while emperipolesis was not identified. Systemic evaluation was unremarkable. He was treated with oral prednisone, which was discontinued due to steroid-induced hyperglycemia, and methotrexate 15 mg/week, achieving approximately 60% improvement of symptoms at 6 months. Conclusion: CRDD may present atypically, and the absence of emperipolesis does not exclude the diagnosis. Careful clinicopathologic correlation and immunohistochemical analysis are essential for accurate diagnosis and guiding individualized therapy.