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Biomedical subjects

S K Ma

Publications and source records attributed to S K Ma.

At least 127 records · Page 7Linked to original sources
PubMed1998

Myelodysplastic syndrome with myelofibrosis and basophilia: detection of trisomy 8 in basophils by fluorescence in-situ hybridization.

We report a case of myelodysplastic syndrome (MDS) with myelofibrosis and pulmonary tuberculosis who had marked basophilia in the peripheral blood. A clonal karyotypic abnormality characterized by trisomy 8 was demonstrated by cytogenetic analysis. By correlation of cell morphology with results of fluorescence in situ hybridization using a chromosome 8 probe, we demonstrated that the basophils were not reactive but belonged to the neoplastic MDS clone.

Adult↗
PubMed1997

Structure/function relationship study of Tyr14 and Arg22 in trichosanthin, a ribosome-inactivating protein.

Amino acids Tyr14 and Arg22 in trichosanthin are residues on helix A1 close to the active-site cleft. They are invariant in various type-I and type-II ribosome-inactivating proteins. In this study, Tyr14 was changed to Phe and Arg22 to Lys and Leu. Modified proteins were purified, and activities compared by assaying their median inhibitory concentration (ID50) on a rabbit-reticulocyte-lysate protein-synthesis system. While the ID50 of wild-type trichosanthin was 0.02 nM, those for [Phe14], [Lys22], [Leu22] and [Phe14, Leu22]trichosanthin were 0.10, 0.03, 0.25 and 0.15 nM, respectively. Therefore, compared with Tyr14, Arg22 appears to play a more important role in trichosanthin. Structural studies on [Leu22]trichosanthin showed that two water molecules occupy the space left by the side chain of Arg22, and hydrogen bonds exist between these water molecules and nearby residues to retain the conformation. The use of intermolecular rather than intramolecular hydrogen bonds may have an adverse effect on stability or folding of the protein and results in a mild decrease in activity.

Abortifacient Agents, Nonsteroidal↗
PubMed1997

Hematological features and treatment outcome in acute myeloid leukemia with t(8;21).

We analyzed the hematological features and treatment outcome in 18 patients with t(8;21) acute myeloid leukemia (AML) diagnosed in Queen Mary Hospital, Hong Kong. They comprised 15 cases of M2, two cases of M4 and one case of M1 according to FAB criteria. Auer rods (17 cases) and dysgranulopoietic features (15 cases) were very frequently observed. Two cases showed marrow eosinophilia while blast cells in one patient demonstrated erythrophagocytic activity. Chromosome changes in addition to t(8;21) were seen in 14 patients, the most common of which was loss of a sex chromosome (10 cases). Of the 14 patients treated with intensive chemotherapy, 13 (93 per cent) entered complete remission with a median event-free survival (EFS) and overall survival (OS) of 11 and 24 months respectively. The probability of EFS and OS at 3 years were 33 +/- 14.3 per cent and 55.1 +/- 15.6 per cent respectively with a median duration of follow-up of 22 months. When compared with AML having no t(8;21) treated similarly in the same period, we could not demonstrate a better clinical outcome for t(8;21) AML.

Adolescent↗
PubMed1997

Clinical presentation, hematologic features and treatment outcome of childhood acute lymphoblastic leukemia: a review of 73 cases in Hong Kong.

Seventy-three consecutive cases of childhood acute lymphoblastic leukemia (ALL) diagnosed and managed in Queen Mary Hospital over a 10-year period from 1985 to 1994 were retrospectively analysed for their presenting features and treatment outcome. The 48 boys and 25 girls ranged in age from 0.4 to 14.2 years (median: 4.3 years). Bone and joint pain was a relatively common presenting feature besides fever, hepatosplenomegaly and lymphadenopathy. Immunophenotyping of blast cells showed: 51 B-cell precursor ALL, one B-ALL, 10 T-ALL and three myeloid-antigen positive ALL. Eight cases were unclassified since immunophenotyping had not been performed. Out of the 73 patients, treatment outcome was analysed in 20 cases treated with UKALL-VIII regimen and 28 cases treated with either the UKALL-XI regimen or the Hong Kong Children Cancer Study Group (HKCCSG) protocol which was modelled upon UKALL-XI. Although complete remission rates were similar between the two groups, patients treated with the former regimen that was less intensified suffered more relapses than the latter (56 per cent versus 21 per cent, P = 0.04). There were, however, no significant differences both in event-free survival (38.2 +/- 11.2 per cent versus 71.3 +/- 9.3 per cent, P = 0.12) and overall survival (70.0 +/- 10.2 per cent versus 79.6 +/- 8.3 per cent, P = 0.41) between the two groups at 3 years by long-rank test. With the use of risk-directed therapy and improved supportive care, two-thirds of our patients are able to enjoy long-term event-free survival.

Adolescent↗
PubMed1997

Cytogenetic abnormalities in pediatric myelodysplastic syndrome: a report of three cases.

Three consecutive cases of pediatric myelodysplastic syndrome (MDS) diagnosed over a three-year period in Queen Mary Hospital, Hong Kong, were described. Depending on the classification system used, they comprised two cases of chronic myelomonocytic leukemia (CMMoL) of which one can be reclassified as juvenile chronic myeloid leukemia (JCML) and one cases of refractory anemia with excess of blasts (RAEB) or an alternative diagnosis of atypical CML. Cytogenetic abnormalities were detected in all of them on examination of bone marrow cells. Of the two CMMoL, one had monosomy 21, whereas the other had hypodiploidy. The patient with RAEB had a complex karyotype of 46,X,del(X)(q24),t(1;7) (p22;q32),add(15)(q26)(8). The balanced translocation (1;7) seen in this patient was exceedingly rare and, to the best of our knowledge, was reported only twice in the literature. The karyotypic abnormalities that we saw in our patients were not well recognized in pediatric MDS. This report emphasizes the importance of cytogenetic study in children suspected of suffering from MDS, which remains a rare disorder of childhood, and a need to rationalize current classification schemes.

Child↗
PubMed1997

Robertsonian translocation as an acquired karyotypic abnormality in leukaemia.

Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality.

Acute Disease↗
PubMed1995

Aggressive pleomorphic CD2+, CD3-, CD56+ lymphoma with t(5;9)(q31;q34) abnormality.

CD56-positive lymphoma is a recently described entity which is characterized by predominantly extranodal involvement and an aggressive clinical course. We report one such case with involvement of the bone marrow and spinal cord at presentation, and associated with reactive hemophagocytic syndrome. The lymphoma cells had a highly pleomorphic appearance which is uncommon in CD56-positive lymphoma. Cytogenetic studies revealed a t(5;9)(q31;q34) abnormality. Analysis of more cases is required to determine if this is a recurring chromosomal translocation characteristic of the group of aggressive CD56-positive lymphoma.

Antigens, CD↗
PubMed1995

B-cell small lymphocytic lymphoma with circulating granular prolymphocytes and a novel trisomy 15 anomaly.

A 53-year-old man presented with cervical lymphadenopathy and massive splenomegaly. Peripheral blood examination showed many prolymphocytes with cytoplasmic azurophilic granules, giving an initial impression of large granular lymphocytosis. The lymph node biopsy and immunohistochemical study findings, however, were more compatible with a diagnosis of B-cell small lymphocytic lymphoma. The circulating prolymphocytes showed restricted kappa light chain expression similar to the lymphoid infiltrate in the lymph node. Karyotypic analysis revealed trisomy 15, a chromosomal abnormality that has rarely been described in small lymphocytic lymphoma or chronic lymphocytic leukemia.

Bone Marrow↗
PubMed1995

Hepatosplenic gamma delta T-cell lymphoma. A distinctive aggressive lymphoma type.

The T-cell receptor (TCR) expressed on the surface of most T-lymphocytes is of alpha beta type, and only a minority bear the gamma delta-TCR. Similarly, postthymic T-cell lymphomas rarely express gamma delta-TCR. Hepatosplenic gamma delta T-cell lymphoma is an uncommon entity that has so far not been widely recognized. We report one such case that has been comprehensively studied by multiple modalities and showed the unique occurrence of leukemic picture at presentation. The 39-year-old man presented with fever, marked weight loss, and massive splenomegaly. Peripheral blood showed thrombocytopenia and a white cell count of 5.8 x 10(9)/l, with 66% medium-sized lymphoid cells that had a round or folded nucleus, condensed chromatin and a moderate amount of pale blue cytoplasm. Splenectomy was performed and histologic examination of the spleen, bone marrow, liver, and abdominal lymph nodes demonstrated lymphoma infiltration with a predominantly sinusoidal pattern. Immunohistochemical studies of the lymphoma cells showed a T-cell phenotype: CD2+ CD3+ CD5+ CD7+ gamma delta-TCR+ alpha beta-TCR- CD56+ CD4- CD8- CD16- CD57-. Cytogenetic studies showed complex clonal chromosomal abnormalities of 44,X, -Y, -11, -22, + mar in 3/16 cells. Rearrangement of the TCR gamma chain gene was demonstrated by polymerase chain reaction; the TCR beta chain gene was partially chain reaction; the TCR beta chain gene was partially rearranged. The patient did not respond to single agent chemotherapy, but achieved clinical remission with combination chemotherapy. Based on the available data in the literature, hepatosplenic gamma delta T-cell lymphoma exhibits distinctive clinicopathologic features, and probably represents the neoplastic counterpart of splenic gamma delta T-lymphocytes. This disease is associated with a poor prognosis and usually relapses despite initial response to chemotherapy.

Adult↗
PubMed1995

Refractory cytopenia with t(1;7),+8 abnormality and dysplastic eosinophils showing intranuclear Charcot-Leyden crystals: a fluorescence in situ hybridization study.

A case of refractory cytopenia and marrow eosinophilia showing t(1;7) translocation and concomitant trisomy 8 is reported. The eosinophils were dysplastic, and showed the unique feature of intranuclear Charcot-Leyden crystal formation, giving rise to a 'lip-like' appearance. We speculate that this unusual cytologic feature resulted from abnormal precipitation of Charcot-Leyden crystal protein in the eosinophils. By fluorescence in situ hybridization using a chromosome 8 specific alpha-satellite probe, the abnormal eosinophils were shown to have derived from the abnormal clone. We postulate that the dysplastic clone might have retained a differentiation potential and be responsive to normal haemopoietic stimuli.

Adult↗
PubMed1993

Acquired immunodeficiency syndrome presenting as marrow cryptococcosis.

Disseminated cryptococcal infection is an uncommon initial manifestation in patients with the acquired immunodeficiency syndrome. The most common sites of involvement by cryptococci are the central nervous system and the lungs, and involvement of the marrow is rare. There are few descriptions in the literature on the cytologic findings of marrow cryptococcosis. We report a patient with disseminated cryptococcosis in which cytologic examination of the marrow provides the first clue to the diagnosis.

AIDS-Related Opportunistic Infections↗
PubMed1993

Megakaryoblastic transformation of polycythemia vera associated with hypercalcemia.

Leukemic transformation is not uncommon in polycythemia vera, particularly after treatment with chemotherapeutic agents. The leukemias that supervene are mostly of myeloid type but megakaryoblastic transformation is distinctly uncommon. We report a case of polycythemia vera terminating in megakaryoblastic leukemia with associated hypercalcemia.

Cell Division↗