Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease): a clinicoradiological profile of three cases including two with skeletal disease.

Originally described as sinus histiocytosis with massive lymphadenopathy, Rosai-Dorfman disease (RDD) is a rare histiocytic proliferative disorder with a distinctive microscopic appearance. A rare entity, RDD is often under-diagnosed because of a low index of suspicion by both radiologist and pathologist. Through this article, we wish to apprise radiologists of the spectrum of disease that can be encountered in this disorder. RDD can mimic other common childhood skeletal diseases including benign Langerhans cell histiocytosis and lymphoma. The clinical and radiological manifestations of RDD vary depending upon organ involvement, and its imaging features are often confused with those of other disorders. RDD should be considered in the differential diagnosis of unifocal and multifocal skeletal involvement caused by granulomatous diseases, infections, pseudogranulomatous lesions and malignancy. As long-term outcome is usually good, a conservative approach is justified in most cases. Contrasted with its typical appearance, presenting with bilateral symmetrical cervical adenopathy (as shown in one patient), we also report extranodal involvement of bone in two patients. Extranodal disease occurs along with concomitant nodal disease in about 43% of patients. In 23% of patients, isolated extranodal RDD can be seen, most commonly in the head and neck. In two of our patients, we observed extranodal involvement with skeletal involvement away from the head and neck not associated with lymphadenopathy. Skeletal involvement in RDD without lymphadenopathy is rare, occurring only in 2% of all the patients reported to date.