Oral signs may be indicative of serious systemic dis-eases. Leukemic infiltration of the gums as the first sign ofleukemia has been rarely reported in the literature, but thistype of oral manifestation requires rigorous evaluation onthe part of the dental professional to provide a diagnosis andreferral for therapy. This case report was submitted andapproved by the Brazilian National Commission on Ethics.A 43-year-old white man was first seen with a complaintof intermittent fever that had been present for 15 days. Healso presented with head and neck lymphadenopathy, rapidweight loss, an increase in volume throughout the length of the marginal gingiva of upper and lower jaws, and his maincomplaint, spontaneous gingival bleeding of moderate in-tensity (Fig 1). After clinical examination, some diagnostichypotheses to gingival lesions were suggested, such as ne-crotizing acute gingivitis, opportunistic infection caused byAIDS, or extramedullary leukemic infiltrate. Additionaltests were required, and panoramic X-ray of the jaw showedno evidence of periodontal resorption. Enzyme-linked im-munosorbent assay test was not reagent and the hemogramconfirmed hemoglobin, 10.5 g/dL; hematocrit, 30.3 percent;leukocytes, 153,000/L with 13 percent of blasts; and plate-lets, 73,000/L.The patient was referred to the hematology monitoring teamand underwent a bone marrow biopsy and incisional biopsy ofthe gingiva. The bone marrow biopsy was conclusive for acutemyeloid leukemia (M5), and histopathological examination ofthe gingival biopsy revealed a mucosa fragment in which theconnective tissue showed a diffuse and hypercellular infiltrate