Table 1.

Summary table of Rosai-Dorfman Disease (RDD)

Etiology	The etiology of RDD is poorly understood at best. There is a suggested link with HHV-6 and EBV but no concrete evidence. Cells with histiocytic linage migrate to lymph nodes and proliferate in a seemingly unregulated manner. This is a distinct entity from Langerhans Cell Histiocytosis with a better prognosis but poorer response to treatment. Emperipolesis is a key feature of RDD, but its function and regulation is not currently understood.
Incidence and prevalence	Specific incidence and prevalence information is not known for this very rare disease with only about 1000 reported cases, however the broader class of histiocytosis type diseases has an incidence of about 3 per million. The disease seems to be less prevalent in persons of Asian descent. Although there is conflicting evidence, RDD may also be more common in those with African descent than Caucasians.
Gender Predilection	There is a strong male gender predilection of approximately 4:1.
Age Predilection	RDD spans all age groups but is most common in the second and third decades of life with a mean age of 20 years at diagnosis.
Risk Factors	There are no clearly defined risk factors for RDD. However extranodal and aggressive disease are more common with a younger presentation.
Treatment	Surgical treatment is the only method with clear efficacy although some success with radiation therapy has been noted and antiviral therapy in early disease holds promise. Chemotherapy is ineffective.
Prognosis	RDD generally has a slow course and most cases spontaneously resolve. Extranodal cases are much more aggressive.
Imagining findings	Nonspecific imaging on CT, MRI and US, similar to inflammatory fibrosing lesions. PET with FDG is strongly positive.