FREQUENCY OF DRUMSTICKS IN NORMAL WOMEN AND IN PATIENTS WITH CHROMOSOMAL ABNORMALITIES

Clinical manifestations of hematologic and oncologic disorders in patients with Down syndrome

Hematologic abnormalities are common in individuals with Down syndrome (DS). Increased erythrocyte mean corpuscular volume (MCV) is frequently found among DS infants and remains elevated throughout life in two-thirds of patients, making interpretation of red cell indices for diagnosis of nutritional anemias or bone marrow failure disorders more challenging. Transient myeloproliferative disorder (TMD) associated with pancytopenia, hepatosplenomegaly, and circulating immature WBCs, is found almost exclusively in DS infants with an incidence of approximately 10%. In most cases, TMD regresses spontaneously within the first 3 months of life, but in some children, it can be life threatening or even fatal. Despite the high rate of spontaneous regression, TMD can be a preleukemic disorder in 20-30% of children with DS. The types of malignancy, response to therapy, and clinical outcome in children with DS are also unique. There is an increased risk of leukemia with an equal incidence of lymphoid and myeloid leukemia. Acute megakaryocytic leukemia (AMKL) subtype is the most common form of acute myeloid leukemia (AML) in this setting, and is uncommon in children without DS. Somatic mutations of the gene encoding the hematopoetic growth factor GATA1 have been shown to be specific for TMD and AMKL in children with DS. Myelodysplastic syndrome can precede AML. Children with DS and leukemia are more sensitive to some chemotherapeutic agents such as methotrexate than other children which requires careful monitoring for toxicity. Although the risk for leukemia is higher in individuals with DS, these patients have a lower risk of developing solid tumors, with the exception of germ cell tumors, and perhaps retinoblastoma and lymphoma.

Higher levels of organization in the interphase nucleus of cycling and differentiated cells

The review examines the structured organization of interphase nuclei using a range of examples from the plants, animals, and fungi. Nuclear organization is shown to be an important phenomenon in cell differentiation and development. The review commences by examining nuclei in dividing cells and shows that the organization patterns can be dynamic within the time frame of the cell cycle. When cells stop dividing, derived differentiated cells often show quite different nuclear organizations. The developmental fate of nuclei is divided into three categories. (i) The first includes nuclei that undergo one of several forms of polyploidy and can themselves change in structure during the course of development. Possible function roles of polyploidy is given. (ii) The second is nuclear reorganization without polyploidy, where nuclei reorganize their structure to form novel arrangements of proteins and chromosomes. (iii) The third is nuclear disintegration linked to programmed cell death. The role of the nucleus in this process is described. The review demonstrates that recent methods to probe nuclei for nucleic acids and proteins, as well as to examine their intranuclear distribution in vivo, has revealed much about nuclear structure. It is clear that nuclear organization can influence or be influenced by cell activity and development. However, the full functional role of many of the observed phenomena has still to be fully realized.

Leukemia in Down syndrome: a review

The incidence of leukemia is higher in children with Down syndrome (DS) than in normals. In approximately 50% of cases the type of leukemia is acute megakaryoblastic leukemia (AMKL) and it occurs during the first 4 years of life. The leukemic cell also has features of erythroid progenitors and therefore appears to be a precursor cell with biphenotypic properties. In addition, newborns with DS frequently develop transient leukemia (TL), which is characterized by the presence of megakaryoblasts in the blood which disappear during the first 1-3 months of life. The incidence of this disorder is unknown although preliminary studies suggest that megakaryoblasts may be found frequently in the blood of DS newborns. TL does not occur in normal newborn infants. Although TL disappears spontaneously, many of these children will develop AMKL at 1-4 years of age. Recent surveys suggest that 20-30% of newborns with TL will develop AMKL. Preliminary evidence suggests that TL is a clonal proliferation, can be fatal, and may occur in a specific subgroup of DS children. The observations in this report are drawn from our own experience, reports in the literature, and data accumulated in the Canadian Down Syndrome Leukemia Registry.

Murine trisomy 16 model of Down's syndrome: central nervous system electron microscopic observations

Murine trisomy 16 is an excellent model for the human Down's syndrome (DS). Electron microscopic (EM) observations were made of the cortical plate within the developing telencephalic vesicle at the gestational age of E17. The EM observations revealed: (A) microtubular profiles which were more coiled and curved in the trisomic condition; (B) poor cell-to-cell apposition and increased cellular membrane fragmentation in trisomy 16; (C) increased nuclear contour irregularity in trisomic neurons; (D) significant decrease in the cross-sectional area of neuronal nuclei in trisomy 16 (p less than 0.01). The microtubular observations lend credence to the hypothesis that abnormal cytoskeletal interactions may underlie the mental deficiency seen in DS and may predispose to the eventual development of Alzheimer's disease (AD) in DS individuals. The cellular membrane findings may be related to reported CNS membrane lipid abnormalities in DS. The nuclear morphologic observations may be related to the reported differences in chromatin and nuclear histone expression in AD. These results strengthen the role of the trisomy 16 mouse as a model for DS and potentially for AD.

Reduced number of peripheral blood granulocytic progenitor cells in patients with Down's syndrome

The number of granulocytic progenitor cells (colony forming units in culture: CFUc) in the blood of patients with Down's syndrome was found to be reduced by 73.2% when compared to a group of age and sex matched controls. However, the blood CFUc of the Down's syndrome patients and the controls showed similar sensitivity to hydroxyurea which suggests that the low number of progenitor cells in Down's syndrome is not compensated by a marked increase in their cellular proliferation. The colony size distributions were similar for both the patients and the controls and, in addition, repeated assays at various intervals revealed no marked fluctuation in the number of blood CFUc in either group. The significance of the reduced number of circulating CFUc in Down's syndrome in relation to the known susceptibility of such patients to leukaemia is discussed.

Klinefelter's syndrome and incontinentia pigmenti Bloch-Sulzberger

We report a newborn with incontinentia pigmenti Bloch-Sulzberger and male phenotype. Chromosome analysis revealed a Klinefelter's syndrome 47,XXY. These findings are compatible with the hypothesis of dominant sexlinked genes carried on the X-chromosome in this disease.

Uveal coloboma and true Klinefelter syndrome

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An XO-X ring X chromosome mosaicism in an individual with normal secondary sexual development

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