MAPK1 and sinus histiocytosis with massive lymphadenopathy: Different viruses have been reported associated with RDD, including Epstein-Barr virus, human herpesvirus-6, and parvovirus B19 infection.29-31 The possible association between RDD and different autoimmune diseases, IgG4-related diseases, have been also reported.32,33 Recent studies have shown Kirsten rat sarcoma viral oncogene homolog (KRAS) and mitogen-activated protein kinase 1 (MAP2K1) mutations in some cases of RDD, suggesting that at least a subset of RDD cases may be clonal lesions, which may open new channels for targeted therapy, particularly in refractory cases.34-37