A 38-year-old man presented with fatigue, dyspnea on exertion and minor bleeding of the gums. Physical examination revealed gum hypertrophy and an extensive petechial rash (Figure 1). His hemoglobin level was 53 (normal 135–175) g/L, his leukocyte count was 110.7 (normal 4.5-11.0) × 109/L and his platelet count was 25 (normal 150–400) × 109/L. He had a normal coagulation profile. A bone-marrow biopsy showed hypercellular marrow with more than 50% monoblasts and promonocytes (Figure 2) that were positive for CD14 and CD64. We diagnosed acute myelomonocytic leukemia. After chemotherapy with daunorubicin and cytarabine, his gum hypertrophy and petechial rash resolved, and his leukocyte count decreased to 0.6 × 109/L. Leukemic cells occasionally infiltrate the central nervous system, skin, liver, spleen or gums in the M3 and M4 types of acute myelogenous leukemia.
Figure 1: Gum hypertrophy and petechial rash on the patient's chest.
Figure 2: Histology image from a bone-marrow biopsy showing hypercellular marrow with promonocytes (black arrow), monoblasts (white arrow) and myelocytes (arrowheads) (hematoxylin–eosin stain, original magnification × 100).
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