Acute Myeloid Leukemia With RBM15-MKL1 Presenting as Severe Hepatic Failure

A 1-month-old girl was transferred to our hospital with marked abdominal distension. She was born to a healthy mother at 39 weeks' gestation, and her postnatal course was unremarkable. On admission, she was afebrile and exhibited hepatomegaly with considerable ascites, causing respiratory failure. Her laboratory results on admission were as follows: white blood cells, 42.5 × 10 9 /L with 1. enhanced computed tomography (CT) showed prominent hepatomegaly with patchy fibrotic areas and narrowing of the intrahepatic portal vein and the inferior vena cava at the hepatic portal area (Figure 1a). Bone marrow examination revealed hypercellularity with dys-plastic erythroid hyperplasia (60% of bone marrow cells) with megaloblastic changes; some of these cells stained positive for periodic acid-Schiff (PAS; Figure 1c). In addition, prominent hemophagocytosis was observed (Figure 1d). By flow cytometric analysis, <5% of total cells were detected in the CD45 low-int /side scatter (SSC) blast gate, and no monoclonal increases of specific populations were observed. She was evaluated for possible causes of acute liver failure including infection, metabolic disorders, and malignancies, but results of blood and urine analysis and culture tests were unre-markable. A liver biopsy could not be performed because of severe condition. A cytological examination of the ascites sample was negative for malignancy, and peripheral blasts had disappeared by day 4 after admission. The patient was treated with pulsed steroids and plasma exchange for hepatic failure of unknown cause. However, her hepatic function and ascites continued to worsen. On day 14 after hospitalization, although her white blood cell count had normalized at 10.1 × 10 9 /L, blast cells were again detected in blood, representing 4% of the white blood cell count. The results of G-banded karyotyping of the initial bone marrow sample revealed t(1;22)(p13;q13). The patient was diagnosed with acute myeloid leukemia (AML) with RBM15-MKL1. A bone marrow aspiration at that time revealed normocellular bone marrow, a decrease in the proportion of dysplastic erythroblasts, and an increase in the monoclonal blast cell count (Figure 1e and f). These blast cells were negative for myeloperoxidase stain and partially positive for PAS stain. Flow cytometric analysis demonstrated that the proportion of CD41-and CD61-positive cells increased, whereas that of CD71/CD235a double-positive cells decreased compared to the counts obtained in the initial bone marrow analysis (Figure 2a and b). Array comparative genomic hybridization (aCGH) using SurePrint G3 Human CGH microarrays 4 × 180 K (Agilent Technologies) revealed the amplification at …