A 3-year-old Thai boy suffered from two histiocytoses, Rosai-Dorfman disease (RDD) and juvenile xanthogranuloma (JXG). The patient first presented with massive cervical lymphadenopathy at the age of one year. Biopsy revealed typical RDD; abnormally large CD68- and S-100 protein-positive histiocytes with occasional emperipolesis filled up the sinuses. Two years later, he developed polyuria and polydypsia. Skull film demonstrated osteolytic lesions at the occiput and left parietal region. Enlargement of the pituitary stalk was found on the magnetic resonance imaging. Despite the clinical impression of Langerhans cell histiocytosis, biopsy of the occipital lesion disclosed numerous large histiocytes with foamy cytoplasm. Several Touton giant cells with wreath-like arrangement of the nuclei were also observed. The abnormal cells expressed CD68 and factor XIIIa, but were non-reactive with S-100 protein and CD1a. Biopsy of the pituitary stalk was not performed. According to the authors’ literature search, this represents the first report of RDD and JXG affecting the same person.

Keywords: Rosai-Dorfman disease, Juvenile xanthogranuloma, Langerhans cell histiocytosis, Histiocytosis