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Biomedical subjects

L C Chan

Publications and source records attributed to L C Chan.

At least 163 records · Page 9Linked to original sources
PubMed1993

Transient myeloproliferative disorder in a Down's neonate with rearranged T-cell receptor beta gene and evidence of in vivo maturation demonstrated by dual-colour flow cytometric DNA ploidy analysis.

Neonates with Down's syndrome may develop a transient myeloproliferative disorder (TMPD) which on presentation is indistinguishable from acute leukemia, with the difference manifest only on follow-up. The clinical course is one of spontaneous remission in TMPD and relentless progression in leukemia. We describe a Down's neonate presenting with hyperleucocytosis and circulating blasts which were positive for CD34, myeloid (CD33), megakaryocytic (CD41, CD42b, CD61), and T-lineage (CD3, CD7), but not B-lineage, associated antigens. Clonal rearrangement of the T-cell receptor beta (TCR beta) gene was found, with the immunoglobulin heavy chain gene in germline configuration, showing the disease to be a clonal proliferation of a multipotential stem cell involving the myeloid and T lineages. Dual-colour flow cytometric DNA ploidy analysis of CD41 positive blasts showed initially a predominant 2N population, but polyploidization to 6N and 8N cells was found on follow-up, concomitant with a progressive decrease in circulating blasts, suggesting maturation of the abnormal clone and a provisional diagnosis of TMPD. This was shown by the eventual resumption of normal haemopoiesis with the disappearance of blasts and the clonally rearranged TCR beta gene.

Bone Marrow↗
PubMed1992

Deletion 12p in de novo acute myeloid leukemia. An association with early progenitor cell.

Deletion of the short arm of chromosome 12 as the sole karyotypic abnormality was found in three cases of acute myeloblastic leukemia (AML). In contrast to what has previously been reported in the literature, none of our cases had an antecedent history of myelodysplasia or toxic exposure, and basophilia was absent. Two cases were terminal deoxynucleotidyl transferase (TdT) positive, suggesting involvement of an early progenitor cell.

Adult↗
PubMed1992

Cytogenetic analysis of hematologic malignancies in Hong Kong. A study of 98 cases.

The karyotypes of 98 patients between the ages of 8 and 81 years with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and chronic myeloid leukemia (CML) are presented. Although the well-described cytogenetic abnormalities associated with particular FAB subtypes in the West were observed, certain important local differences were noted. In ALL, hyperdiploidy was rarely observed, whereas the Philadelphia chromosome was observed in 50% of abnormal karyotypes. In AML, the t(8;21) was infrequently observed in M2 case, whereas trisomy 4 and 6, rarely reported elsewhere, formed 12% of the abnormal cases. In MDS, the incidence of -5/5q- and/or -7/7q- was 83% of cases with aberrant cytogenetic findings. Neither i(17q) nor an extra Ph was seen in 26 cases of CML including 9 cases of accelerated phase/blast crisis. In addition, previously unreported cytogenetic abnormalities occurring as single cases are presented. These findings are discussed in the context of geographical heterogeneity of chromosomal abnormalities in leukemia and emphasize the importance of continued epidemiologic studies of cytogenetics in hematologic malignancies.

Adolescent↗
PubMed1992

Translocation (12;17)(p11-12;q11-12): a recurrent primary rearrangement in acute leukemia.

We identified two patients with acute leukemia in relapse (one lymphoblastic and the other with evidence of mixed lymphoid-myeloid differentiation) with t(12;17)(p12;q11) as the primary karyotypic abnormality. There are six previously reported cases of acute leukemia with an identical or similar translocation. To our knowledge, t(12;17) has not been reported in other forms of neoplasia. A review of these cases suggests that t(12;17) carries a poor prognosis.

Adolescent↗
PubMed1992

Isochromosome 14q and leukemia with dysplastic features.

We report a case of chronic myelomonocytic leukemia (CMMoL) with unusual features and an isochromosome 14q as the sole abnormality. A review of the literature suggests that isochromosome 14q (or trisomy 14) is a marker of leukemia with dysplastic features.

Anemia, Refractory, with Excess of Blasts↗
PubMed1992

Homozygous pyruvate kinase deficiency in Hong Kong ethnic minorities.

Three cases of pyruvate kinase (PK) deficiency resulting in congenital haemolytic anaemia with transfusion dependency are described. These cases resulted from consanguineous marriages in non-Han Chinese and include a pair of twins. We believe this to be the first documentation of homozygous PK deficiency in the Hong Kong population. The diagnosis was masked due to transfusion dependency in each case stressing the need to take a sample of pretransfusion blood for PK enzyme assay, and for family studies, when this disorder is suspected.

Anemia, Hemolytic↗
PubMed1992

Detection of clonal Epstein-Barr virus in malignant proliferation of peripheral blood CD3+ CD8+ T cells.

Epstein Barr virus (EBV) DNA was detected in a monoclonal proliferation of T cells in a three-year-old girl who presented with a history of fever, hepatosplenomegaly, and generalised lymphadenopathy. The disease ran a rapid, fulminant course and the patient died 11 days after presentation. Examination of the blood showed a lymphocytosis of 50 x 10(9)/l with all the cells showing the morphology of large granular lymphocytes. These cells were CD2+3+8+25+. Cytogenetic studies showed the presence of a 6q- clone. Southern blotting and hybridisation with a constant region probe for the T-cell receptor (TCR) beta chain gene showed clonal rearrangement of the TCR beta gene. Hybridisation of the Southern blot to the EBV XhoI probe revealed a clonal pattern of episomal EBV DNA. Our results establish the association between clonal EBV infection to a malignant proliferation of peripheral blood CD8+ T cells.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Use of technicon H*1 technology in routine thalassaemia screening.

In a retrospective study of 36 cases of alpha-thalassaemia trait, 43 cases of beta-thalassaemia trait and 45 cases of iron deficiency, we have assessed the performance of the Technicon H*1 erythrogram, the hypochromia minus microcytosis (H-M) index, and the discriminant function (DF). The diagnostic accuracy of the erythrogram pattern was 83.3% for alpha-thalassaemia trait and 95.3% for beta-thalassaemia trait. The diagnostic accuracy for the H-M index was 19.4% for alpha-thalassaemia trait, 72.1% for beta-thalassaemia trait and 91.1% for iron deficiency. By comparison, the DF gave a diagnostic accuracy of 75.0% for alpha-thalassaemia trait, 81.4% for beta-thalassaemia trait and 88.9% for iron deficiency when using a locally derived value for the constant (k) = 19.2. Our study shows that the H*1 erythrogram pattern, the H-M index and the DF are useful predictive indicators in routine laboratory screening for thalassaemia.

Discriminant Analysis↗
PubMed1992

Concomitant presence of trisomy 21 and del(9q) in acute myeloid leukemia.

We report two cases of acute myeloid leukemia with deletion of the long arm of chromosome 9 [del(9q)] and trisomy 21. del(9q) and +21 do not often occur as a sole karyotypic abnormality in acute myeloid leukemia (AML). Their concomitant presence is rare; the significance of the findings in leukemia is discussed.

Adolescent↗
PubMed1991

Nasopharyngeal carcinoma: role of marrow biopsy at diagnosis.

Twenty-seven new patients with advanced nasopharyngeal carcinoma were evaluated by marrow biopsy at diagnosis. The marrow trephines and blood clots were evaluated by morphology and immunohistochemical studies for cytokeratin and found negative in all cases. The median follow-up of this group of 27 patients was 22 months, and 7 of them had relapsed in the skeletal system. We conclude, in view of its poor sensitivity, that routine use of marrow biopsy for the staging of nasopharyngeal carcinoma is not recommended.

Biopsy↗