Retrospective nationwide survey of pediatric RDD in Japan: a high prevalence of mutations in the kinase pathway genes.

Background: Rosai-Dorfman-Destombes disease (RDD) is a rare form of histiocytosis, characterized by the accumulation of S100 protein-positive and CD1a-negative histiocytes with emperipolesis. Recently, oncogenic mutations in mitogen-activated protein kinase pathway genes were reported in nearly half of RDD patients.

Methods: We conducted a nationwide retrospective survey of childhood RDD in Japan.

Results: We found nine patients (five boys and four girls) with a median age at diagnosis of 8 years and 3 months (range, 9 months to 15 years 5 months). Two patients had nodal lesions only, three had extra-nodal lesions only, and four had both. PD-L1 was expressed in all cases. Two were resolved without treatment. Three were treated with prednisolone, one with surgery and radiation, and three with chemotherapy. Two were complicated by glomerulonephritis. Somatic pathogenic mutations in the kinase pathway genes were found in five of the six patients analyzed (three in MAP2K1, one in KRAS, and one in TSC1). Two chemotherapy-resistant patients with MAP2K1 mutations responded to trametinib. Within a median follow-up of 4 years and 9 months, two died of disease.

Conclusion: Most children with RDD carry mutations in the kinase pathway genes. Mutation analysis is suggested for patients with refractory disease.