A Rare Case of Transformation of Childhood Myelodysplastic Syndrome to Acute Lymphoblastic Leukemia
An 8-yr-old girl was transferred to our hospital for further evaluation of severe pancytopenia that was discovered 4 days earlier at a local hospital, to which she had been admitted for fever persisting for 2 weeks. Her hemoglobin was 6.0 g/dL, white blood cell (WBC) count was 0.9×109/L, and platelet count was 71×109/L. She had mild, easy bruising on both legs and night sweating. At admission, the patient had an acute ill appearance without fever and showed no splenomegaly, lymphadenopathy, or organomegaly on physical examination. A complete blood cell count (CBC) test showed hemoglobin of 5.8 g/dL, WBC count of 2.4×109/L, and platelet count of 214×109/L. A peripheral blood smear revealed severe normocytic normochromic anemia with mild anisocytosis and poikilocytosis, including some dacrocytes, moderate neutropenia (absolute neutrophil count of 0.78×109/L) with left shifting, and a few giant platelets. Her reticulocyte count was in the reference range (1.11%) and nucleated red blood cells (RBC) were observed (1/100 WBCs). Schistocytes were not observed. Most biochemical tests for liver and renal function tests were within the reference intervals, except increased serum lactate dehydrogenase (LDH; 638 IU/L, reference interval, 218-472 IU/L) and alkaline phosphatase (ALP; 506 IU/L, reference interval, 95-280 IU/L). Serum C-reactive protein (CRP) was slightly increased at 5.3 mg/L (reference interval, 0-5.0 mg/L). Urinalysis results were not specific except a few WBCs, 3-5/high-power field.\nBM aspirate smears and touch print preparation of the BM biopsy revealed hypercellular marrow with dysplastic changes in 3 hematopoietic cell lineages. Erythroid dysplasia, including nuclear budding, multinuclearity, and nuclear irregularity, was present in 15% of all erythroid precursors (). Granulocytic dysplastic changes, including megaloid change, hyposegmentation, and hypogranularity of the cytoplasm, was present in 15% of granulocytic cell lines. Megakaryocytes were adequate in number and exhibited dysplastic changes, including unequivocal micromegakaryocytes, separated nuclear lobes, and non-lobulated or round nuclei in 10% of all megakaryocytes. Myeloblasts accounted for 0.8% of nucleated cells in the BM. A BM biopsy section exhibited nearly 100% cellularity with a marked increase of erythroid precursor cells. Dysplastic changes in all hematopoietic cell lines were the same as in BM aspirates. Few histiocytes were observed in the biopsy section ().\nThe pathologic findings of aplastic anemia or BM failure diseases such as adipocytosis and hypocellular or acellular marrow were not observed. Flow cytometric analysis for CD55 and CD59 performed to rule out paroxysmal nocturnal hemoglobinuria revealed normal levels of CD55 and CD59 in both RBC and WBC. Epstein-Barr virus real-time quantitative PCR and parvovirus B19 IgM tests revealed no evidence of viral infection. Nutritional deficiencies and metabolic diseases were excluded based on medical history and physical examination.\nCytogenetic analysis of the BM revealed a normal karyotype (46, XX). No cytogenetic abnormalities were detected in FISH analysis with probes for EGR1 (5q-), D7S486 (7q-), CEP8 (trisomy 8), and D20S108 (20q-). The patient was diagnosed as having refractory cytopenia of childhood (RCC) based on the 2008 WHO classification system. She received only supportive treatment in our hospital. After her general condition recovered, she was discharged and followed up with CBC and liver function tests.\nThree months after the initial diagnosis of MDS, she was re-admitted to our hospital because of a relapse of high fever. A CBC test revealed hemoglobin of 9.4 g/dL, WBC count of 410.5×109/L, and platelet count of 15×109/L. A peripheral blood smear revealed severe microcytic hypochromic anemia, marked leukocytosis with many leukemic blasts (90%), and severe thrombocytopenia. The results of several biochemistry tests were increased as follows: AST, 134 IU/L; ALT, 74 IU/L; ALP, 498 IU/L; LDH, 11,306 IU/L; CRP, 54 mg/L.\nBM aspirate smears () and a biopsy section () revealed a markedly hypercellular marrow that had been completely replaced by small leukemic blasts (95%). Normal hematopoietic cells were markedly decreased. Cytochemical staining demonstrated that the cells were all negative for myeloperoxidase (MPO), Sudan black B (SBB), and periodic acid-Schiff (PAS). Flow cytometric immunophenotyping revealed that the blasts expressed B lymphoid markers that were CD10 (+), CD19 (+), CD79a (+), cytoplasmic IgM (+), and terminal deoxynucleotidyl transferase (TdT) (+). The myeloid cell markers of CD13 and CD33 and T cell markers of CD2, CD5, and CD7 were not expressed. Karyotype analysis of BM leukemic cells revealed normal chromosomes (46, XX). BCR-ABL, E2A-PBX, and TEL-AML gene rearrangements were not detected using reverse transcription-PCR and FISH analyses. MLL gene rearrangements and p16 (9p21) deletion analysis by FISH were also not detected.\nBased on the 2008 WHO classification system, the patient was diagnosed with B lymphoblastic leukemia not otherwise specified that was transformed from childhood MDS-refractory cytopenia. She received chemotherapy beginning the day after BM examination. Unfortunately, her general condition deteriorated rapidly due to tumor lysis syndrome during chemotherapy. She expired from hyperkalemia on the third day of chemotherapy.\nRetrospectively, we analyzed the purified mononuclear cell fractions of the first (MDS-diagnosed) and second (ALL-diagnosed) BM specimens using microarray analysis, Affymetrix Cytogenetics Whole Genome 2.7 Mb Array (Affymetrix, Santa Clara, CA, USA) to identify genetic abnormalities. In the first BM sample, no chromosomal or genetic abnormalities were observed. However, in the second BM sample, we found several large interstitial deletions of 27 Mb and 5.7 Mb on 5q21.2q31.1 and 13q14.1q21.1, respectively, and many microdeletions on chromosomes 5q, 12q, 13q, and 22q. Particularly, a partial homozygous loss of 200 kb was observed in a region of heterozygous loss on chromosome 13q14.1q21.1 in the second BM sample. The chromosome views of the second BM sample using cytogenetic microarray analysis are shown in . To confirm this result, additional FISH analysis of the second BM sample was performed using 2 probes for EGR1 (5q31) and RB1 (13q14), and produced the same result: 5q31.2 was not deleted and 13q14.3 was deleted in 84% of the examined nuclei ().