A healthy four-year-old Italian boy was hospitalized due to a skin superinfection of an isolated right laterocervical lymphadenopathy (7x4cm), which had appeared four months earlier. In the previous months, he had normal haematochemical examinations except for a slight in-crease in ESR, negative infectious serologies, Mantoux and quantiferon tests, normal chest X-rays and abdominal ultrasound. A neck ultrasound showed right laterocervical lymphadenopathy with a homogeneous iso-hypoechoic structure, poor cortico-medial differentiation and lively centre-hilar intralymphnode vascularisation. During his admission an intravenous antibiotic therapy was started with a good response. A neck MRI was performed showing multiple partially abscessed lymphadenopathies. Bone marrow aspirate resulted normal and the lymphnode biopsy showed a typical pattern for Rosai-Dorfman leading to the diagnosis. To rule out extra-nodal localisations, a total-body MRI was performed, which proved negative. A close clinical-ecographic follow-up was set up, showing a progressive spontaneous dimensional reduction of the lymphadenopathy in the following months. Rosai Dorfman disease is a rare non-Langerhans cell histiocytosis. It typically presents with bilateral laterocervical adenopathy and frequent extranodal localisations. It affects children and young adults with a slight prevalence in the male sex and those of African ethnicity. Its diagnosis is histological and staging is performed with a total body MRI. The prognosis is excellent for isolated cutaneous and nodal forms. Steroid therapy, chemotherapy and immunosuppressants are treatment options for multifocal forms, but no guidelines exist yet. This case is therefore atypical in terms of age, ethnicity and (unilateral) localisation.