LAUSR

Rosai-Dorfman disease (RDD) is an uncommon benign histiocytic proliferative disorder characterized by massive bilateral cervical lymphadenopathy [1]. More than 40% of RDD patients have extranodal lesions in locations such as the skin, orbit, respiratory tract and bones [2]. Of these extranodal lesions, cutaneous lesions are the commonest. We report an RDD patient with subcutaneous, nasal, pharyngeal and fibular lesions. Notably, the subcutaneous lesions showed spontaneous regression, whereas the other extranodal lesions persisted. A 37-year-old woman presented at our outpatient clinic with a month-long history of bilateral lymphadenopathy of the neck and multiple subcutaneous nodules of the limbs (figure 1A, B). Her personal and family history was unremarkable. She reported recurrent fever over two months, nasal obstruction and left ankle pain for six months. 18F-fluorodeoxyglucose PET-CT revealed multiple lesions on the limbs and cervical lymph nodes (figure 1C). Masses were also found in the nasal cavity, pharynx and fibula (figure 1D-F). The nasal and fibular lesions were accompanied by osteolytic changes. Blood tests demonstrated hypochromic anaemia and hypergammaglobulinaemia. A biopsy specimen from a subcutaneous nodule revealed numerous large histiocytic cells with a pale cytoplasm and hypochromatic nuclei in the hypodermis. Prominent emperipolesis (engulfment of lymphocytes) was also observed (figure 1G, H). These histiocytes were positive for CD68 and S100, and negative for CD1a. IgG4+ plasma cells were not found. A biopsy specimen taken from a nasal lesion showed similar pathological findings. Based