Rosai-Dorfman disease (RDD) is an uncommon disorder, characterized by an atypical expansion of histiocytes which classically shows emperipolesis and immunoreactivity with S-100 protein.
Rosai-Dorfman disease (RDD) is an enigmatic histiocytic disorder classically diagnosed by a distinctive combination of pathological features: emperipolesis, or migration of intact haematological cells through the voluminous cytoplasm of lesional histiocytes, and expression of S100 by these histiocytes.
Immunohistochemical studies showed that the histiocytes expressed CD163 and S100, while ERG and D2-40 highlighted their intralymphatic confinement, ultimately leading to the diagnosis of intralymphatic RDD.
Herein, we describe a patient carrying a high titer of autoantibodies to interferon (IFN)-γ with disseminated Mycobacterium kansasii infection presenting with emperipolesis and Rosai-Dorfman disease (RDD)-like histopathological features characterized by remarkable, large, pale-staining "RD cells", which were CD68 and S100 positive and CD1a negative.
Histopathologic evaluation of the specimens revealed inflammatory lesions containing atypical S100-immunoreactive histiocytes diagnostic of Rosai-Dorfman disease, but not an increase in the IgG4-positive plasma cells.