Takayoshi Itoh

Effects of anti-platelet glycoprotein Ib and/or IIb/IIIa autoantibodies on the size of megakaryocytes in patients with immune thrombocytopenia.

Abstract: To determine whether anti‐platelet autoantibodies react with megakaryocytes, as well as with platelets, in immune thrombocytopenia (ITP), 38 ITP patients were studied. They were classified into four groups; anti‐platelet glycoprotein lb‐positive (group A, n> = 5), anti‐platelet glycoprotein II/b/IIIa‐positive (group B, n = 2), positive to both antibodies (group C, n = 3), and negative to both antibodies (group D, n = 28). The number and size of megakaryocytes in each group were compared. The number of megakaryocytes in groups A, B, C, and D was 12.8 ± 8.9, 75.2, 29.1, and 17.0 ± 21.7/mm2, respectively. The mean cytoplasmic area of megakaryocytes in groups A, B, C, and D was 1001 ± 26.3, 1621, 1109, and 1311 ± 235.6/μm2, respectively. This finding indicated that, in the presence of anti‐platelet glycoprotein Ib, megakaryocytes were not increased in number and were small in size, whereas, in the presence of anti‐platelet glycoprotein Ilb/IIIa, megakaryocytes were increased in number and in cytoplasmic area. Our study suggested that anti‐platelet glycoprotein Ib may impair platelet production by megakaryocytes in ITP.

Megakaryopoiesis in patients with cyclic thrombocytopenia

Summary Megakaryopoiesis was examined in 10 patients (eight females and two males) with cyclic thrombocytopenia (CT) to investigate the underlying pathogenesis. Numbers of CFU‐Meg and megakaryocytes and the mean cytoplasmic area (mean area) of megakaryocytes at the peak, nadir, ascent mid phase, and descent mid phase of the platelet cycle were determined. The patients were classified as female cases group I (cases 1–4; previously diagnosed as ITP and CT occurred during remission), female cases group II (cases 5–8; persistent CT from initial diagnosis), and male CT (cases 9 and 10). In three of the four female cases in group I, numbers of CFU‐Meg and megakaryocytes were normal or increased persistently during the platelet cycle, whereas the mean area fluctuated in synchrony with the platelet cycle, suggesting failure of cyclic production rather than platelet destruction. In the female cases in group II and one female case in group I, numbers of CFU‐Meg and megakaryocytes were also normal or increased at four phases of the cycle, but the mean area did not fluctuate, remaining large during the cycle, suggesting cyclic destruction or platelet clearance. In contrast, in the male patients values for numbers of CFU‐Meg, megakaryocytes and mean cytoplasmic area fluctuated during the platelet cycle, indicating that cyclic changes in megakaryopoiesis generated the platelet cycle. These findings indicate that the measurement of cytoplasmic area is useful for distinguishing cyclic platelet production from cyclic destruction or clearance in CT.

Simultaneous measurements of megakaryocyte-associated IgG (MAIgG) and platelet-associated IgG (PAIgG) in chronic idiopathic thrombocytopenic purpura.

Abstract: We have simultaneously measured platelet‐associated IgG (PAIgG) and megakaryocyte‐associated IgG (MAIgG) in 30 untreated patients with chronic idiopathic thrombocytopenic purpura (CITP). Megakaryocytes were purified from bone marrow by 35% Percoll gradient centrifugation, followed by negative immunopanning using magnetic immunobeads. The normal range of MAIgG in 30 healthy donors was 15.5 & 10.0 ng/105 megakaryocytes, whereas MAIgG in the 30 CITP patients was 140 & 59.3 ng/105 megakaryocytes, although the values were widely distributed. From the PAIgG and MAIgG data, CITP patients were classified into three types; type I (PAIgG < 200 ng/107 platelets and MAIgG < 150 ng/105 megakaryocytes), type II (PAIgG > 200 ng and MAIgG > 150 ng), and type III (PAIgG < 200 ng and MAIgG > 150 ng). Patients with types I and III had good clinical courses, but, in contrast, patients with type II responded poorly to steroid therapy followed by splenectomy or became refractory to treatment. In splenectomized patients, MAIgG of responder was promptly decreased to normal range and, in contrast, that of non‐responder was persistently elevated. These results indicate that anti‐platelet autoantibodies are able to bind with megakaryocytes in the bone marrow as well as with platelets in the peripheral blood, and the results also suggest that megakaryopoiesis in CITP is heterogeneous. Simultaneous measurement of PAIgG and MAIgG may predict the clinical outcome of CIPT.

Therapy-Related Acute Myeloid Leukemia 6 Years after Clonal Detection of inv(11)(q21q23) and MLL Gene Rearrangement

Results of recent studies with animal models suggest that expression of MLL fusion proteins promotes acute leukemogenesis. However, the most potent MLL fusion proteins are not sufficient for the development of acute myeloid leukemia (AML). The clinical data on the pathogenesis of this type of leukemia are limited.We analyzed the case of a patient with therapy-related AML with MLL rearrangement. The patient initially developed AML with t(8;21). Although the patient achieved complete remission with chemotherapy, an abnormal karyotype, inv(11)(q21q23), was detected. After 6-year persistence of a clone with the inversion 11 karyotype in the bone marrow, secondary AML developed. Results of fluorescence in situ hybridization analysis combined with magnet-activated cell sorting analysis showed that MLL rearrangement was detected in CD34+ and CD13+ fractions but not in a CD3+ fraction of the bone marrow.There were 2 important clinical findings. One was that MLL rearrangement was not sufficient for the development of leukemia. The other was that MLL rearrangement targets specific lineages.

Non-Hodgkin's lymphoma followed by plasmacytoma, both arising in A thyroid gland with Hashimoto's disease.

We describe here a rare case of malignant lymphoma followed by plasmacytoma in Hashimotos thyroiditis. The patient developed malignant lymphoma (small, non-cleaved cell, and non Burkitts type by Working Formulation classification), and remained in remission for 2 years after receiving combination chemotherapy, and then developed plasmacytoma in the same lesion. Rearrangement bands for IgH from both specimens showed different bands, indicating that both were of monoclonal type but of a different clonal origin. Considering the clinical course in this case, thyroidectomy may be indicated for lymphoproliferative diseases in Hashimotos thyroiditis treated with chemotherapy.