A 9 year-old boy presented with sore gingivae of one month's duration. Oral clinical examination revealed diffusely swollen buccal, palatal (fig. 1) and lingual gingivae. The deciduous teeth were very mobile. Physical examination showed cervical lymphadenopathy and a recent blood test mild anemia. Premature root resorption and extensive upper and lower alveolar ridge bone resorption were observed on dental X-ray (fig. 2). The provisional diagnosis included Langerhans cell histiocytosis and acute myelocytic leukemia. Histological examination of biopsy material taken from the lower molar gingivae revealed a mixed inflammatory infiltrate consisting of lymphocytes, neutrophils, plasma cells and small numbers of eosinophils (fig. 3).