Rosai-Dorfman Disease: A Rare Disease with Uncommon 18F-FDG PET CT Findings.

Rosai-Dorfman disease (RDD) also called as sinus histiocytosis with lymphadenopathy is a rare benign histiocytic proliferative disorder of unknown etiology and was first described in 1969 with the incidence of 1 in 200,000. Most commonly present with lymphadenopathy with around 40 percent presented with extranodal involvement such as skin, central nervous system, nasal cavity, and bones. Bone involvement is rare and it is <10% cases of RDD. We present a case of RDD with extranodal involvement such as nasal cavity, cutaneous nodules, paraspinal lesion with intraspinal extension, and uncommon appendicular skeleton involvement (tibia and fibular involvement).