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Biomedical subjects

L C Chan

Publications and source records attributed to L C Chan.

At least 127 records · Page 7Linked to original sources
PubMed1995

Essential thrombocythemia: a retrospective analysis of 39 cases.

Thirty-nine Chinese patients presenting as essential thrombocythemia (ET) were analyzed retrospectively. The median age at presentation was 69 years and the M:F ratio was 1.35:1. At diagnosis, 33 cases (84%) were asymptomatic and the diagnosis was made incidentally, while 3 cases (8%) presented with small vessel, and 2 cases (5%) with large vessel, thrombosis. One patient (3%) presented with minor bleeding. The platelet count ranged from 0.9-34 x 10(12)/l. Of 12 karyotypes done, 2 cases were abnormal, both showing the Philadelphia (Ph) chromosome. First-line therapy was radiophosphorus (32P) in 3 cases, melphalan in 20 cases, and hydroxyurea in 12 cases; 4 cases did not receive specific therapy. During the follow-up (mean = 4 years), no thrombotic or bleeding episodes were observed. One patient with the Ph chromosome underwent blastic transformation. These results indicate that bleeding and thrombosis occur significantly less in Chinese patients than in Western patients. The Ph chromosome appears to be a bad prognostic indicator. Because of the very low incidence of complications and good prognosis, the authors believe that cytoreductive therapy is best achieved by the use of hydroxyurea instead of alkylating agents or radiophorphours, as the latter agents are potentially leukemogenic.

Adult↗
PubMed1995

Large granular lymphocyte leukemia. A study of nine cases in a Chinese population.

Large granular lymphocyte (LGL) leukemia is a neoplastic disorder of lymphocytes that is characterized by the presence of prominent cytoplasmic granules, and involves the proliferation of at least two distinct cell types, T cells and natural killer (NK) cells. The authors report the clinical and pathologic features of 9 Chinese patients with LGL leukemia, who represented 14% of 64 cases of chronic lymphoproliferative disorders diagnosed at their centers in 3 years. Three different groups could be defined on immunophenotypic and clinical grounds. The first group of 4 cases were CD2+CD3+CD4-CD8+. With the exception of a pediatric case, these cases ran an indolent course that was similar to the T-cell LGL leukemia most common in Western patients. However, thrombocytopenia and pure red cell aplasia were more common in the patients in this study, which was similar to the experience in Japanese patients. The second group of two cases were CD2+CD3+CD4+CD8-, and appeared to have worse outcomes than the first group. The third group of 3 cases were CD2+CD3-CD4-CD8-CD56+. Although phenotypically similar to the NK-cell LGL leukemia reported in Western patients, these cases were clinically more aggressive than their Western counterparts. This study is the first to report comprehensively the different types of LGL leukemias in Chinese patients, and provides useful information on the similarities and similarities and differences of these disorders as compared to those cases in the West.

Adult↗
PubMed1995

Intensive consolidation chemotherapy for newly diagnosed acute myeloid leukemia using a regime containing moderate dose cytosine arabinoside and mitoxantrone.

Fifty patients with previously untreated acute myeloid leukemia were treated with an induction regimen consisting of cytosine arabinoside 100 mg/m2 per day by 18 h i.v. infusion for 7 days, daunorubicin 50 mg/m2 per day by i.v. bolus injection for 3 days and etoposide 75 mg/m2 per day by 1 h i.v. infusion for 7 days. Thirty seven of them (74%) went into complete remission (CR) and they all then received two consecutive courses of consolidation chemotherapy consisting of cytosine arabinoside 500 mg/m2 per day by 1 h i.v. infusion every 12 h for 4 days (total eight doses) and mitoxantrone 12 mg/m2 daily by 30 min i.v. infusion for 3 days. They were followed by maintenance chemotherapy with cytosine arabinoside and thioguanine 2 monthly. With a median follow up time of 24 months, 20 of the 37 complete responders had relapsed (54%). The disease-free survival (DFS) of 37 CR patients and the overall survival of all patients at 24 months were 37 and 44%, respectively. Age of patients and number of courses of induction chemotherapy to achieve CR were significant factors predicting DFS. Myelosuppression was the major toxic side effects. Ten patients had prolonged marrow suppression following consolidation chemotherapy. In conclusion, despite the significant myelosuppression observed, overall improvement in treatment outcome was not demonstrable with the use of this intensive consolidation therapy.

Adolescent↗
PubMed1995

Comparison of haemoglobin H inclusion bodies with embryonic zeta globin in screening for alpha thalassaemia.

AIMS: To compare the haemoglobin (Hb) H inclusion test with immunocytochemical detection of embryonic zeta chains in screening for alpha thalassaemia. METHODS: Blood samples from 115 patients with relevant clinical history and hypochromic microcytic indexes were screened using the HbH inclusion test and the Variant Hemoglobin Testing System (BioRad, Hercules, CA, USA). RESULTS: The HbH inclusion test was positive in 61 of 115 cases, three of whom had HbH disease confirmed by electrophoresis. The remaining 58 had alpha thalassaemia 1. All three HbH cases and 56 of 58 cases of alpha thalassaemia 1 expressed embryonic zeta chains, giving a specificity of 96.7%. Fifty four of 115 cases had a negative HbH inclusion test, of whom 50 had beta thalassaemia trait and three had iron deficiency. No diagnosis was reached for the remaining patient. CONCLUSION: The immunocytochemical test is as sensitive as the HbH inclusion test in screening for alpha thalassaemia. The presence of zeta chains is highly specific for alpha thalassaemia 1 incorporating the (--/SEA) deletion. The specificity and simplicity of the immunocytochemical test make it the test of choice in screening for alpha thalassaemia.

Base Sequence↗
PubMed1994

Hereditary hemolytic anemia caused by diverse point mutations of pyruvate kinase gene found in Japan and Hong Kong.

We identified four distinct point mutations in homozygous pyruvate kinase (PK) variants in Japanese and Chinese patients with chronic nonspherocytic hemolytic anemia. All gene abnormalities were missense mutations that caused single amino acid substitutions. 1261A (Q421K) and 1436A (R436H), which were identified in PK Sendai and PK Shinshu, had been found in unrelated Japanese and Amish PK variants, respectively. The clinical severity and extremely low residual erythrocyte PK activity of PK Shinshu as well as of the Amish PK might be caused partly by aberrant splicing, because the 1436A mutation changes a nucleotide at the last nucleotide in the exon 10. Recently, we diagnosed a 42-year-old Japanese woman with chronic nonspherocytic hemolytic anemia as having a homozygous PK deficiency. DNA sequencing of the variant PK gene showed a homozygous missense mutation at 1403GCT-->GTT, resulting in a single amino acid substitution from 468la-->Val. The gene mutation is likely to impair the allostericity of this enzyme, speculated from the tertiary structure. A homozygous missense mutation in PK Hong Kong, a boy of a non-Han southern Chinese minority group, was identified in exon 7 of the human L-PK gene, 941ATT-->ACT, resulting in a single amino acid substitution from 314lle-->Thr. The R-PK activity is expected to be severely affected, because the mutated amino acid residue is located between the 313 Lys and the 315 Glu, which are very important for acid-base catalysis and magnesium binding, respectively. Both the R- and M2-type PK were shown by polyacrylamide gel electrophoresis of the PK Hong Kong erythrocyte lysate, and this is the first report of a homozygous individual whose erythrocytes contain the immature (M2)-type isozyme.

Adult↗
PubMed1994

The spectrum of chronic lymphoproliferative disorders in Chinese people. An analysis of 64 cases.

BACKGROUND: Chronic lymphoproliferative disorders are considered rare in Oriental patients and are thought to constitute only 2% of all leukemias in these patients, compared to 20-30% in Western patients. We conducted a retrospective analysis of Chinese patients with chronic lymphoproliferative disorders to define the frequency and spectrum of these disorders. METHODS: A consecutive series of Chinese patients with leukemia and lymphoproliferative disorders seen at two regional hospitals in Hong Kong were analyzed retrospectively. The diagnosis of chronic lymphoproliferative disorders was based on morphologic and immunologic criteria proposed by the French-American-British Cooperative Study Group. RESULTS: Sixty-four Chinese patients with chronic lymphoproliferative disorders were identified, and these patients constituted 19% of a total of 342 cases of leukemia diagnosed in 3 years. Chronic lymphocytic leukemia was the most common form, occurring at a frequency of 12.5% of all leukemias. The clinicopathologic features of these patients were similar to those of Western patients, except that Chinese patients tended to present with more advanced (Rai's Stages III and IV; Binet's Stage C) and bulky (splenomegaly > 9 cm) disease, and expressed lambda light chain about six times more frequently. Other chronic lymphoproliferative disorders identified in this study included prolymphocytic leukemia, mantle zone lymphoma, hairy cell leukemia, splenic lymphoma with villous lymphocytes, large granular lymphocyte leukemia, and Sezary syndrome. The authors did not identify any case of human T-cell lymphotropic virus-I-related lymphoproliferative disorders within the study period. CONCLUSION: In addition to providing the frequencies of various chronic lymphoproliferative disorders in southern Chinese people, this study also showed that these disorders no longer should be considered rare in this population. Inherent biologic differences between lymphoproliferative disorders in Chinese and Western patients also may exist.

Adult↗
PubMed1994

Trisomy 12 in chronic lymphocytic leukemia. An interphase cytogenetic study by fluorescence in situ hybridization.

B-cell chronic lymphocytic leukemia (CLL) is a rare disorder in the Chinese population. We evaluated the use of fluorescence in situ hybridization (FISH) with a chromosome 12-specific probe in the detection of trisomy 12 in interphase cell of 19 Chinese CLL patients. FISH successfully detected trisomy 12 in two cases, one of which had normal conventional cytogenetic findings, giving an incidence of 10%. The low incidence of trisomy 12 in our CLL patients may also reflect a biologic difference of this rare disorder in our population, compared to that of the West.

Adult↗
PubMed1994

Cytogenetic triclonality in acute myeloid leukemia: a morphologic, immunologic and in situ hybridization study.

Cytogenetically unrelated clones are uncommon in hematologic malignancies. We report a case of acute myeloid leukemia, which consisted morphologically of two populations of small and large blasts demonstrating immunophenotypic heterogeneity. Cytogenetic analysis showed 3 karyotypically abnormal clones: 47,XY, +14/45,XY,dic(5;17)(q11;p11),14dmin, and a near-tetraploid clone. In situ hybridization showed that the near-tetraploid clone corresponded to the large blasts, and the near-diploid clones the small blasts, therefore demonstrating a direct relationship between cell size and DNA content. The diverse morphologic, immunologic and cytogenetic heterogeneity observed in our case suggested hematopoietic oligoclonality.

Aged↗
PubMed1994

Inversion (14)(q11q32) in childhood T-cell acute lymphoblastic leukemia.

Inversion (14)(q11q32) is a common cytogenetic aberration in T-cell chronic lymphoid malignancies but is rare in T-cell acute lymphoblastic leukemia (T-ALL). We describe two cases of childhood T-ALL in which inv(14)(q11q32) was present concomitantly with other karyotypic aberrations typical of T-ALL. The possible significance of inv(14) in these cases is also discussed.

Child↗
PubMed1994

Biphenotypic leukemia with t(9;11)(p22;p15).

Translocation (9;11)(p22;p15) was found in a patient with acute biphenotypic leukemia. This has not been reported previously although both chromosome bands 9p22 and 11p15 have been involved in a variety of leukemias with diverse phenotypes.

Adult↗
PubMed1994

Flow cytometric measurement of glycosylphosphatidyl-inositol-linked surface proteins on blood cells of patients with paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder of hematopoiesis in which affected cells are deficient in glycosylphosphatidyl-inositol (GPI) anchored surface proteins. The authors used flow cytometry to study 10 patients with PNH. They used a comprehensive panel of monoclonal antibodies against all nine currently known GPI-linked surface proteins (CD14, CD16, CD24, CD48, CD55, CD58, CD59, CD67, CD73) on cells of various lineages. Deficient cells were identified in the granulocytic-monocytic and erythroid lineages in all patients. However, the lymphoid lineage was affected in only eight patients. The patterns of deficiency were variable, with deficient cells constituting a part to all of the cells in the lineages tested. Certain proteins, including CD16, CD58, and CD59, appeared to be preferentially expressed, despite severe deficiencies of other GPI-linked proteins. Moreover, a trimodal pattern of expression of CD16, CD48, and CD59 was observed, in which a population of cells with intermediate levels of expression were identified in addition to positive and deficient cells. The authors' findings indicated a great degree of heterogeneity in the patterns and levels of expression of the GPI-linked proteins in the various cell types, as well as a possible heterogeneity in lineage involvement. The different patterns of expression of GPI-linked proteins should be considered when using flow cytometry to diagnose PNH. Finally, the clinical progression in some of the patients suggested a possible link between PNH, aplastic anemia, and myelodysplasia.

Adult↗
PubMed1994

Involvement of eosinophils in acute myeloid leukaemia with monosomy 7 demonstrated by fluorescence in situ hybridization.

Monosomy 7 is the commonest monosomy in acute myeloid leukaemia (AML). A patient with AML and monosomy 7 was investigated by fluorescence in situ hybridization. Monosomy 7 could be demonstrated in the blasts and also in mature eosinophils, but apparently not in lymphocytes. Monosomy 7 may occur in a multipotential myeloid progenitor cell as part of the multi-step leukaemogenic process.

Aged↗
PubMed1994

Trisomy 14, deletion 20q and t(3;3) (q21;q26) in a case of myelodysplastic syndrome with myelofibrosis.

We describe a patient with trilineage myelodysplasia and hyperplastic megakaryopoiesis associated with significant myelofibrosis at diagnosis, who developed acute myeloid leukaemia two months afterwards. The clinical and pathological features were consistent with a myelodysplasia/myelofibrosis syndrome with leukemic transformation. Cytogenetic investigation showed trisomy 14, del(20q) and t(3;3) (q21;q26). These findings are of possible significance in the understanding of the association between myelodysplasia and myelofibrosis.

Chromosome Deletion↗
PubMed1994

High incidence of thrombophilia detected in Chinese patients with venous thrombosis.

Venous thromboembolism is rare in Chinese. To determine the incidence and disease profile of thrombophilia in Chinese patients with thrombosis, 52 unselected Chinese patients with documented venous thrombosis were studied for the presence of thrombophilia. Levels of antithrombin III (AT III), protein C (PC) and protein S (PS) as well as the presence of acquired lupus anticoagulant (LA) and anticardiolipin antibody (ACA) were investigated. Thirty patients were found to be abnormal. These consisted of 5 AT III deficiencies, 9 PC deficiencies, 10 PS deficiencies, 1 combined PC & PS deficiency (all in the heterozygous range), and 5 patients with LA and/or ACA. When the patients with LA and/or ACA are excluded, the incidence of hereditary thrombophilia is 25/47 i.e. 53.2% which is much higher than those reported in studies of Caucasian patients selected under strict criteria. Family studies performed in 16 cases of hereditary thrombophilia revealed involvement in 11 cases (68.7%); a total of 36 heterozygous family members were affected, most of which remain asymptomatic. Although 35 events predisposing to thrombosis (27 pregnancies, 1 oral contraceptive consumption and 7 surgical operations) were identified among these index patients, and the heterozygous family members, thrombosis was observed on only 6 occasions (17.1%). The data suggest that pregnancy and surgery do not carry the same degree of thrombotic risk in Chinese as in the Caucasian population with heterozygous AT III, PC and PS deficiency.

Adolescent↗
PubMed1994

Poor outcome of intensive chemotherapy for adult acute lymphoblastic leukemia: a possible dose effect.

Fifty consecutive adult patients with acute lymphoblastic leukemia (ALL) were treated with an intensive cyclical chemotherapy and the mean received dose of individual cytotoxic drug was retrospectively studied. The median age was 28 years. Twenty-one (43%) had white blood cell (WBC) count over 30 x 10(9)/l. Of the 26 patients with successful cytogenetic studies, ten (28%) had unfavorable clonal chromosomal abnormalities (four Philadelphia chromosome, six others). A high complete remission (CR) rate (86%) was achieved. This was associated with delivery of 100% of the planned dosage of vincristine, prednisone, and daunorubicin at induction. Dose reduction of asparaginase, the fourth drug in the induction protocol, was recorded in 20 (40%) patients. The CR rate of these patients was not adversely affected. Dose reduction was recorded during consolidation (38 of 43 remitters) and maintenance (18 of 20 remitters) as a result of treatment toxicity. The mean received dose of teniposide, Ara-C, asparaginase, mercaptopurine, and methotrexate was 73% (SD 7%), 73% (SD 7%), 62% (SD 41%), 65% (SD 15%) and 73% (SD 17%) of the planned dosage, respectively. The 5-year overall survival and leukemia-free survival (LFS) were 11% (95% CI: 0-27%) and 13% (95% CI: 0-26%), respectively. Even standard-risk patients had 4-year LFS of only 26% (95% CI: 0-57%). Among 36 remitters not withdrawn from consolidation, there were 29 treatment failures after a median follow-up of 42 months; 25 (86%) of these were leukemia relapse, three (10%) were toxic death during consolidation, and one patient (4%) died from therapy-related myelodysplastic syndrome. We postulate inadequate drug delivery during postremission therapy contributed to the high relapse rate in the whole group as well as the standard-risk patients.

Adult↗