Unrelated donor bone marrow transplantation for acute mixed lineage (myeloid and B-lymphoid lineage) leukemia in an adult with Down syndrome

This article describes a rare case of bone marrow transplantation (BMT) from an unrelated donor (URD) in an adult Japanese male with Down syndrome (DS) diagnosed as having acute mixed lineage leukemia. Examination of peripheral blood demonstrated WBC 6.2 x 10(9)/l with 45.5% blasts at admission. Leukemic blasts with positive peroxidase stain, but negative periodic acid-Schiff stain comprised 91.6% on bone marrow specimen. Surface marker analysis of these blasts showed the following: CD3(-), CD5(-), CD7(-), CD10(+), CD19(+), CD13(+), CD14(-), CD33(+), CD34(+), CD41a(-), and CD56(-). Based on these data, he was diagnosed as having acute mixed lineage (myeloid and B-lymphoid lineage) leukemia. He achieved complete remission (CR) by lymphoid-oriented chemotherapy performed after ineffective myeloid-oriented therapy. After four courses of consolidation chemotherapy for lymphoid lineage blasts, recurrence due to proliferation of myeloblasts had occurred. Thereafter, a second CR was obtained by low dose cytosine arabinoside (AraC) therapy. As this patient was considered to have a high risk of relapse, we selected allogeneic BMT from URD. Severe stomatitis due to methotrexate (MTX) occurred probably due to altered pharmacokinetics usually observed in DS patients. Though acute graft-versus-host disease (GVHD) of systemic skin (grade II) and pneumonia were observed during neutropenia due to the post-conditioning regimen, he could be discharged from our hospital on the 135th day after BMT. On day 205 post-BMT, however, bronchiolitis obliterans (BO) occurred as a chronic GVHD disorder. Despite therapy with prednisolone and FK506, he died on day 400 post-BMT because of respiratory failure due to BO. In DS patients, superfluous toxicities due to MTX and AraC treatment have been reported, and these toxicities have been considered due to altered pharmacokinetics in patients with DS. This patient could tolerate the transplant conditioning regimen commonly used in patients without DS.     

Cerebellar myeloblastoma formation in CD7-positive, neural cell adhesion molecule (CD56)-positive acute myelogenous leukemia (M1)

 We present a first report of a CD7⁺ acute myelogenous leukemia patient who developed intracranial myeloblastomas. The patient was neurologically normal on physical examination at presentation. The peripheral leukocyte count was extremely high (203.6×10⁹/l). The blasts expressed CD7 and CD56 (neural cell adhesion molecule) in addition to CD13, CD33, CD34, and HLA-DR. The karyotype of bone marrow cells was normal. The patient was diagnosed as having acute myelogenous leukemia (AML, M1). Following a short period of complete remission, bone marrow relapse and meningeal leukemia occurred, and the patient died of respiratory failure. Autopsy revealed that blasts had invaded the subarachnoid space and cerebellum, and two myeloblastomas were found in the cerebellar hemisphere. Both CD7⁺ and CD56⁺ AML have been reported to have a high incidence of central nervous system involvement. CD7⁺ CD56⁺ AML calls for prophylaxis of central nervous system leukemia. Received: 2 May 1997 / Accepted: 17 July 1997     

Acute myeloid leukemia originating from the same leukemia clone after the complete remission of acute lymphoid leukemia

A 22-year-old female was diagnosed as having acute lymphoid leukemia (ALL) in February 1995, from the findings of peroxidase negative, CD10+, CD19+, TdT+ and rearrangement of IgH and TCR beta. AdVP (doxorubicin, vincristine and prednisolone) therapy achieved a complete remission (CR). Bone marrow transplantation had to be abandoned because of the lack of an HLA-identical donor. Intensification therapy was thus carried out repeatedly. In June 1998, myeloblast with Auer rods, peroxidase positive, CD13+, CD33+ and HLA-DR+, appeared. The patient was diagnosed as having lineage switch acute myeloid leukemia (AML) from ALL. Though A-DMP (cytosine arabinoside, daunorubicin, 6-mercaptopurine) therapy was resistant, AdVP therapy led to a CR. The patient died of cardiotoxicity from anthracyclines in February 1999. From the results of the Ramasamy method using the clonal rearrangements of the Ig heavy chain gene locus, the origin of the pathological cells of ALL and AML was indicated to be the same leukemia clone.     

CD7(+) acute myeloid leukemia (M0) associated with a mediastinal bulky mass lesion

A 41-year-old man visited his doctor in May 2000 because of a sore throat and high fever. His symptoms did not improve, despite administration of antibiotics and nonsteroidal anti-inflammatory drugs. Since a chest X-ray examination revealed an anterior mediastinal bulky tumor, he was referred and admitted to our hospital on June 21, 2000. The peripheral white blood cell count was 44,540/microliter with 74% myeloblasts. Bone marrow aspiration revealed a hypercellular marrow with 82% myeloblasts, which were negative for peroxidase and alpha-naphthyl butylate esterase staining. Blast cells were positive for CD7, CD13, CD33, CD34, and HLA-DR, and negative for CD56. A needle biopsy specimen of the mediastinal tumor consisted of myeloblasts. We diagnosed the patient as having CD7 (+) acute myeloid leukemia (AML) (M0) with a bulky mediastinal mass based on the surface marker analysis, although the clinical features resembled myeloid/NK precursor acute leukemia. The patient achieved a complete remission after two courses of induction therapy. We are planning an allogeneic stem cell transplantation during his first remission because of the high risk of relapse.     

An autopsy case of acute mixed lineage leukemia with monosomy 7 in a child

A five-year-old boy initially diagnosed common ALL was developed to acute myelomonocytic leukemia. At onset, the bone marrow was hypercellular and 77% of the cells were blasts, mainly lymphoblast-like cells and cytogenetic study demonstrated 45, XY, -7 in all blasts. Cytochemically most of those blasts were negative for peroxidase, sudan black B, alpha-NB esterase staining. The immunological phenotype was J5 (CD10)+, I2 (HLA-DR)+, SmIg-, CyIgmu-, Leu1 (CD5)-, OKT11 (CD2)-, MY7 (CD13)-, suggesting common ALL. Eight months later, the bone marrow cells were occupied with large sized blasts which were almost positive for peroxidase stain and the cells showed coexpression of Mo1 (CD11b)+, MY4 (CD14)+, MY7+, MY9 (CD33)+, MCS2 (CD13)+, I2+, J5-, B4 (CD19)-, Mo2 (CDw14)-, at relapse. He died 2 years and 6 months after his initial diagnosis. An autopsy was performed which revealed generalized infiltration of leukemic cells and aspergillosis of the lung. In general, monosomy 7 is associated with myelodysplastic syndrome in childhood, and is terminated to acute myeloblastic leukemia. In this case, bone marrow blasts demonstrated monosomy 7 cytogenetically, and this case was considered as an acute mixed lineage leukemia of bilineal type. And this case proved that a monosomy 7 can also be terminated to acute mixed lineage leukemia with both lymphoid and myeloid phenotypes.     

Refractory anemia terminating in acute megakaryoblastic leukemia (M7)

A 72-year-old man with refractory anemia (RA) developed overt megakaryoblastic leukemia after the course of RA with excess of blasts. The blasts were positive for platelet peroxidase activity and had platelet glycoproteins (GPs) such as GPIIb/IIIa and GPIIIa. The bone marrow biopsy at terminal stage disclosed marked fibrosis. The nature of the megakaryoblasts was investigated. The blasts did not differentiate morphologically into mature megakaryocytes with TPA addition. In vitro colony assay showed the failure of colony-forming unit, megakaryocyte growth in peripheral blood. The pathogenesis of myelofibrosis in our patient is discussed.     

Acute myelomegakaryocytic leukemia developed from myelodysplastic syndrome after chemotherapy against complicated small cell lung cancer]

A patient with acute myelomegakaryocytic leukemia (AMMgL), which developed from myelodysplastic syndrome (MDS) after chemotherapy against complicated small cell lung cancer, is reported. The patient was a 66 year-old male, who first presented with moderate macrocytic anemia. Bone marrow aspiration showed absolute erythroid hypoplasia and morphological abnormalities were found in erythroid, granuloid and megakaryocytic lineage cells. Iron utilization studies using radioisotope showed ineffective hematopoiesis. He was diagnosed as having MDS (refractory anemia) and treated with prednisolone, fluoxymesterone, and transfusions. After 3 years, small cell lung cancer was found, but he achieved complete remission with chemotherapy. Since then, pancytopenia progressed with myelofibrosis. Abnormal blasts were found in peripheral blood and gradually increased. He finally died from a blastic crisis resulting in gastric bleeding. The blasts were peroxidase negative, platelet peroxidase positive (10%), and glycoprotein II b/III a antibody positive, indicating megakaryoblasts.     

Essential thrombocythemia transformed to acute myeloblastic leukemia

A 48-year-old woman was referred to Tohoku University Hospital in November 1981 because of leukocytosis pointed out in a group examination. At that time white blood cell count was 26.8 x 10(3)/microliters with no blasts, platelet count 268.0 x 10(4)/microliters and hemoglobin 11.4 g/dl. Bone marrow aspirates showed marked increase of megakaryocytes (15,900/microliters). Bone marrow chromosome analysis revealed 46, XX, -18, +mar without Ph1 chromosome, and DNA analysis showed no bcr rearrangement. She was diagnosed as having essential thrombocythemia and was treated with busulfan. On November 1986, she developed remarkable leukocytosis with leukemic blasts. White blood cells reached 153 x 10(3)/microliters with 33% blasts. Her blasts were positive for peroxidase staining, but negative for platelet peroxidase on electron microscopic study and platelet specific glycoproteins. A diagnosis of acute myeloblastic leukemia (M2) was made. The patient received various combination chemotherapy, which was ineffective, and she died due to pneumonia on June, 1989. In Japan, there has been reported only 8 cases of essential thrombocythemia transformed to acute leukemia. The clinical pictures of these 9 cases were discussed.     

CD 56-positive acute myeloid leukemia (AML-M 1) with t(16;21) (p11;q22) presenting an extramedullary tumor in the right breast at relapse

A 46-year-old woman was diagnosed as having acute myeloid leukemia (M 1) with translocation t(16;21) (p11;q22). The leukemic cells were positive for CD 13, CD 33, CD 34, CD 41, CD 56 and HLA-DR. After induction chemotherapy, the patient achieved complete remission (CR). However, 8 months later she relapsed with various additional chromosomal abnormalities. Although the patient achieved a 2nd CR after re-induction chemotherapy, the patient had extramedullary tumors in the right breast twice and relapse occurred frequently. The tumor cells were characterized by the same immunophenotypes and t(16;21) with additional 1 q trisomy. Although there was no evidence of hematological relapse, another type of 1 q trisomy was observed. Furthermore, an increase of abnormalities with 1 q trisomy was noted concomitant with re-increase in the number of blasts. The patient underwent allogeneic bone marrow transplantation (BMT), but she died from BMT complications. The case could have been a karyotype of t(16;21) with additional chromosomal abnormalities through consecutive approaches. Because of the high occurrence rate of relapse, we consider various additional chromosomal abnormalities and the expression of CD 56 as prognostic factors of this condition.     

Conversion of acute leukemia from a T-lymphoid to a myeloid phenotype

A 7-year-old girl with an acute leukemia was reported whose blasts showed conversion from a T-lymphoid to a myeloid phenotype. At the onset of the disease, the blasts were negative for peroxidase and displayed FAB L1 morphology. Surface marker analysis revealed only CD7 antigen. Although complete remission was achieved, an extramedullary relapse was identified as having a several subcutaneous tumors 15 months later. Tumor cells showed the same marker expression as that of the blasts at the onset. After short term culture without an addition of any differentiation stimulators, the blast cells expressed CD2, CD3, CD4, CD8, and CD25 antigens. The karyotype was 46, XX, t(12; 21) (p11; q22). The intensive chemotherapy and radiation therapy were carried out, however, a hematological relapse occurred 12 months later. At this time, the blasts were strongly positive for peroxidase and expressed HLA-DR and CD33 antigens with disappearance of the CD7 antigen. Chromosome analysis revealed the additional abnormalities (del (7) (p15), -17, +der (17) t (17;?) (p13;?].     

Lineage switch in acute leukemia

Conversions of leukemic cell lineage (lymphoid or myeloid) have been reported only rarely. Our review of the cytochemical and immunophenotypic features of 89 cases of childhood leukemia in marrow relapse indicated lineage switch (lymphoid to myeloid or the reverse) in six patients (6.7%). Five patients with acute lymphoblastic leukemia (ALL) at diagnosis had converted to acute nonlymphoblastic leukemia (ANLL), and one had converted from ANLL to ALL. Each child received lineage-specific multiagent chemotherapy when initially diagnosed, and all achieved a complete remission. After conversion, four patients readily achieved second remissions with treatment for the phenotype evident at lineage switch. Two patients with ANLL at conversion failed ALL-directed reinduction, while one of the two responded to high-dose cytarabine but died during bone marrow hypoplasia, emphasizing the importance of prompt recognition of lineage switch and selection of an appropriate plan of retreatment. Cytogenetic studies disclosed evidence of clonal selection in one patient and clonal stability in two. These findings indicate an unexpectedly high frequency of lineage switch in patients who relapse in the bone marrow after intensive chemotherapy. Although specific causative factors could not be identified, our observations suggest at least two general mechanisms for lineage switch in acute leukemia. In one, chemotherapy appears to eradicate the dominant clone present at diagnosis, permitting expansion of a secondary clone with a different phenotype. In the second, drug-induced changes in the original clone may either amplify or suppress differentiation programs so that phenotypic shift is possible.     

Immunophenotypic transformation from acute undifferentiated leukemia to Burkitt's-like acute lymphoblastic leukemia

Progression of more differentiated to less differentiated malignant phenotypes has been described infrequently during the natural evolution or at relapse of treated hematopoietic malignancies. This report describes an unusual instance of immunophenotypic transformation from an immunologically undifferentiated acute leukemia to a leukemia that at relapse possessed morphologic and immunologic markers characteristic of a Burkitt's-like acute lymphoblastic leukemia. A 26-year-old man initially presented with pancytopenia and a bone marrow diffusely replaced with blast cells morphologically most consistent with a French-American-British L2 subclassification. The surface immunophenotype of the blasts at diagnosis showed HLA-DR surface antigen but no myeloid, lymphoid, or immunoglobulin determinants. Despite successful induction and ongoing consolidation chemotherapy, the patient had a relapse five months after diagnosis; blast cells at relapse demonstrated marked cytoplasmic vacuolation consistent with a Burkitt's-like L3 acute lymphoblastic transformation. Immunophenotypic analysis revealed the presence of restricted immunoglobulin determinants (mu heavy chain and kappa light chain), as well as two separate B lineage surface determinants (BA-1 and B-1). Immunophenotypic transformations may reflect the presence of either a multiclonal or multipotent leukemic population; documentation of the frequency of such transformations and genomic analysis of the transformed subpopulations may be helpful in furthering the understanding of molecular mechanisms involved in leukemogenesis.     

The value of intracellular CD41 antigen detection to the diagnosis of acute megakaryoblastic leukemia]

An 11-month-old boy was transferred to our hospital because of fever and bleeding tendency on March 13, 1998. Laboratory studies showed a white blood cell count of 43,360/microliter with 75% blasts, a hemoglobin concentration of 8.4 g/dl, and a platelet count of 23 x 10(3)/microliter. Surface marker analysis with a flow cytometer revealed that only 21% and 11% of the blasts, respectively, were positive for CD41 and CD42b. Treatment with a permeabilizing agent apparently increased the reactivity of the blasts with anti-CD41 monoclonal antibody (MoAb), which can recognize IIb independently of IIIa. However no significant differences were observed in reactivity with anti-CD41 MoAb (which recognizes the IIb/IIIa complex) anti-CD61 MoAb and anti-CD42b MoAb before or after fixation. Blasts positive for platelet peroxidase were observed by electron microscopy, thus confirming the diagnosis of acute megakaryoblastic leukemia. We concluded that the detection of intracellular antigens is useful for the quick diagnosis of acute megakaryoblastic leukemia characterized by low surface expression of megakaryocytic lineage antigens.     

DBMP-85 was effective at diagnosis and LVP was effective at relapse in a case of acute mixed leukemia

A 16 year-old boy was admitted to our hospital in April 1985, because of bilateral submandibular swellings. Hematological examination revealed Hb was 7.3 g/dl, WBC was 89,000/microliters (76% blast), and platelet was 154,000/microliters. His bone marrow was hypercellular and consisted with 91% blasts. Myeloperoxidase staining was positive for 38% of blasts. Auer rods were seen in some of blasts. Thus, the diagnosis was M1 according to FAB classification. Cytogenetic studies of 20 marrow cells were performed and all cells had 46, XY, -1, -7, 3q-, 7q-, 17q+, +2mar. Eighty five percent of blasts expressed HLA-DR and 43% of blasts expressed CD2 and CD13 simultaneously. Thus, this leukemia was considered as the hybrid type of acute mixed leukemia by surface marker analysis. DBMP-85 regimen, the chemotherapy for AML, was started after admission and complete remission (CR) was attained in June 1985. After 4 courses of post remission chemotherapy, he discharged in December 1985 and was followed at our outpatient clinic without chemotherapy. His disease was relapsed in June 1986, and the combination chemotherapy with mitoxantrone, etoposide and Ara-C was applied to him but failed to attain CR. Then, LVP protocol, the chemotherapy for ALL, was started and CR was achieved. The blasts at relapse had morphologically myeloid features, and expressed HLA-DR, CD2 and CD13 as well as at diagnosis. Cytogenetic studies at relapse showed some karyotype except gaining 12p- anomaly. Therefore, same blasts were considered to emerge at relapse. Our case suggests that LVP therapy may be effective for AML expressing myeloid and lymphoid surface markers.     

The c-sis gene expression in cells from a patient with acute megakaryoblastic leukemia and Down's syndrome

The c-sis gene expression in leukemia cells from a patient with acute megakaryoblastic leukemia and Down's syndrome was studied. The leukemia blasts were identified as megakaryoblasts by the platelet peroxidase reaction and the reactivity against antiplatelet monoclonal antibodies. Leukemia cells obtained from peripheral blood or bone marrow specimens before and after initiation of chemotherapy were analyzed for c-sis gene expression by the RNA-DNA dot blot hybridization. Although the level varied, the mRNA of the c-sis gene was detected in all megakaryoblastic leukemia cells obtained at different clinical stages. The c-sis mRNA level in cells obtained after relapse was higher than that obtained before the initiation of therapy. The 25S c-sis mRNA was detected in a megakaryoblastic leukemia cell line established from this patient. The role of the expression of the c-sis gene in acute megakaryoblastic leukemia cells is discussed.     

Neural cell-adhesion molecule (CD 56)-positive,t(8; 21) acute myeloid leukemia (AML,M-2) and granulocytic sarcoma

A 49-year-old man with t(8; 21) acute myeloid leukemia relapsed 8 months after successful induction chemotherapy with a paraspinal granulocytic sarcoma. There was no evidence of leukemia in the bone marrow at relapse. At initial presentation, the blasts coexpressed CD 15, CD 33, CD 34, CD 45, CD 19, and CD 56 (a neural cell-adhesion molecule). Expression of certain cell-adhesion molecules on leukemic blasts may determine a tendency to develop extramedullary relapse. The co-expression of CD 56 may have a role in the predisposition of t(8; 21) AML to develop GS.     

Acute megakaryoblastic leukemia developing 11 years after diagnosis of essential thrombocythemia

A 57-year-old man was diagnosed to have essential thrombocythemia (ET) in July 1977. He was doing well with continual medication of carboquone but was hospitalized because of slight unconsciousness and gait disturbance in May, 1988. His laboratory data were as follows: WBC count 81,600/microliters with 55% of blasts with cytoplasmic blebs, Hb 10.2 g/dl, and platelet count 2.6 x 10(4)/microliters. Bone marrow aspiration revealed hypercellular marrow with 72.8% blasts. Chromosomal analysis showed tetraploidy with 7p+ and 19p+. Cytochemistry of blasts showed the positivity for platelet peroxidase and CDw 41. The diagnosis of acute megakaryoblastic leukemia was made. Meningeal leukemia was also suspected by the cerebrospinal fluid data, and cytarabine was intrathecally injected. Then the percent of blasts of peripheral blood gradually decreased and the data of cerebrospinal fluid improved. However, several days later the patient became comatose probably due to cerebral bleeding, and died. In this case, two possibilities were considered (1) that a blastic transformation to acute leukemia from ET, and (2) that a secondary leukemia developed as a result of the chemotherapy, independently of ET. Since there was no evidence of myelodysplastic syndrome, it was concluded that this case represented a blastic transformation of ET.     

Flow cytometric analysis of myeloperoxidase negative acute unclassifiable leukemias by monoclonal antibodies. Acute myelogenous and acute megakaryocytic leukemia

Pretreatment peripheral and/or bone marrow blasts from 14 patients with acute unclassifiable leukemia (AUL) expressing myeloid related cell-surface antigen (CDII) or megakaryocyte-platelet related cell-surface antigen (OKM6), were isolated for further analysis in this study. Among 11 cases of CD11+AUL, despite a lack of myeloperoxidase (MPO) activity, one patient's blasts possessed Auer rod in a basophilic cytoplasm and another one's blasts expressed MPO maintaining the same surface phenotype after 20 months of his clinical course. The blast from 2 cases possessed both myelomonocytic and monocyte-specific antigens on the cell-surface, whereas the remaining nine cases completely lacked monocyte-specific antigen which is detectable by monoclonal antibodies, Mo2, My4 and Leu M3 (CD14). In addition, we revealed the presence of MPO protein in the cytoplasm of 3 cases of AUL patients by cytoplasmic immunofluorescence test utilizing monoclonal antibody (MA1). Following these results, the former was diagnosed as acute myelomonocytic leukemia (AMMoL) and the latter as acute myelogenous leukemia (AML) by immunophenotypic analysis using flow cytometry (FACS IV) and cytoplasmic immunofluorescence test. We have also described three cases of acute megakaryocytic leukemia which were demonstrated by the presence of megakaryocyte-platelet-related cell-surface antigens detected by utilizing flow cytometry and monoclonal antibodies in addition to both the PPO activity which was shown by ultrastructural cytochemistry, and the emergence of differentiation antigens while culturing these leukemic cells. The blast of 1 case possessed both platelet GPIb and GPIIb/IIIa cell-surface antigens detected by 5F1 (CD36), AN51 (CDw42), and J15, P2 and HPL2 (CDw41), respectively, whereas the remaining two cases almont lacked the GPIb cell-surface antigen. Hence, the former was diagnosed as immature (pro) megakaryocytic leukemia and the latter as acute megakaryoblastic leukemia from the viewpoint of immunophenotypic analysis as will be discussed in this article. These leukemic blasts did not express both T-cell lineage antigens which are detectable by monoclonal antibodies, T6 (CD1), T11 (CD2), T3 (CD3), T4 (CD4), T1 (CD5), Tp40, Leu9 (CD7), T8 (CD8), and B-cell lineage antigens which are detectable by monoclonal antibodies, B4 (CD19), B1 (CD20), B2 (CD21) and J5 (CD10).(ABSTRACT TRUNCATED AT 400 WORDS)     

The immunologic detection of minimal residual disease in acute leukemia

Certain combinations of differentiation antigens are expressed on leukemia blasts and are absent or extremely rare among normal progenitors in the fetal liver and fetal and regenerating bone marrow. These combinations include cCD3/TdT, a thymic feature retained on thymic-acute lymphoblastic leukemia (T-ALL) blasts outside the thymus, and the coexpression of TdT and myeloid markers (CD13, CD33) on a proportion of ALL and acute myeloid leukemia (AML). Thus, double marker immunofluorescence assays are operationally leukemia-specific and can be applied in 35% of acute leukemias for detecting minimal disease at a less than 10(-4) level; only rare cases, 2 of 35 in our study, switch these relevant features during relapse. The sensitivity and specificity of these assays was tested as follows. First, bone marrow samples taken from patients who had originally presented with blasts expressing the leukemia-associated combinations but were in full morphologic remission were studied, and varying numbers (less than 0.01% to 10% of the mononuclear fraction) of cells with aberrant features were identified in 11.6% of the cases. Second, the outcome of 19 patients with minimal disease identified immunologically while in complete morphologic remission was investigated: all 19 patients have developed systemic relapse within 4 to 25 (median 14.5) weeks. In contrast, 17 of 25 patients also morphologically in complete remission and without residual disease identifiable immunologically after repeated testing are still in morphologic and immunologic remission (follow-up 17 to 114 weeks, median 28 weeks). Only eight patients in this group have relapsed so far: in two patients the relapse was localized in the cerebrospinal fluid, while in six patients a systemic relapse was observed 6 to 51 (median 21.5) weeks after the last negative immunologic bone marrow examination. In conclusion, no false-positive results were detected with these sensitive assays, and the introduction of appropriately planned prospective studies, including the immunologic detection of residual leukemia, is justified on the basis of these observations.     

Infant leukemia with t(1;22) presenting proliferation of erythroid and megakaryocytic cell lineages

We report a case of infant leukemia with the proliferation of both erythroblast and megakaryoblast lineages. The blasts became double-positive for both erythroblastic and megakaryoblastic surface markers at the time of bone marrow relapse. A 9-month-old girl was admitted to our hospital presenting chiefly poor with weight gain and anemia. She also had splenomegaly, pleural effusion, leukocytosis, and thrombocytopenia. A bone marrow specimen showed 53.2% erythroblasts (PAS positive, alpha-NA positive, CD41 negative, MPO negative) and 20.4% megakaryoblasts with marked cytoplasmic blebs. We examined specimens by two-color flow cytometric analysis. At the onset, CD41+ glycophorin A- fraction and CD41- glycophorin A+ fraction were two major components. At the bone marrow relapse, the majority of blasts had altered to double-positive. Chromosomal analysis showed t (1; 22) (p13; q13), which has been reported to be specific for acute megakaryoblastic leukemia (M7) in infants. We reasoned that a leukemia had occurred in this patient at a progenitor cell level common to both erythroid and megakaryocytic lineages.