Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026986 (myelodysplastic syndrome)
 14,926 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dyskeratosis congenita (DC) is an inherited disorder characterized by skin pigmentation, nail dystrophy and mucosal leucoplakia. In 1995 a Dyskeratosis Congenita Registry was established at the Hammersmith Hospital. In the 46 families recruited, 76/83 patients were male, suggesting that the major form of DC is X-linked. As well as a variety of noncutaneous abnormalities, the majority (93%) of patients had bone marrow (BM) failure and this was the principal cause (71%) of early mortality. In addition to BM hypoplasia, some patients also developed myelodysplasia and acute myelod leukaemia. Pulmonary abnormalities were present in 19% of patients. In affected females the phenotype was less severe. Some female carriers of X-linked DC had clinical features. Carriers of X-linked DC showed skewed X-chromosome inactivation patterns (XCIPs), suggesting that cells expressing the normal DC allele have a growth/survival advantage over cells that express the mutant allele. Linkage analysis in multiplex families confirmed that the DKC1 gene, responsible for the X-linked form of DC, is located within Xq28 and facilitated its positional cloning. The high incidence of BM failure in association with a wide range of somatic abnormalities together with the ubiquitous expression of DKC1 suggest that, as well as having a critical role in normal haemopoiesis, this gene has a key role in normal cell biology.
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PMID:Dyskeratosis Congenita (DC) Registry: identification of new features of DC. 1023 44

Hematopoietic stem-cell transplantation (HSCT) is an effective mode of therapy in pediatrics for the treatment of both malignant and non-malignant disorders. We compared the course of children transplanted with unrelated umbilical cord blood (UCB) to those transplanted with allogeneic sibling bone marrow (BM) for bone marrow failure syndromes. Thirteen patients with a median age of 6.3 years were transplanted for the following diseases between April 1992 and November 1997: myelodysplastic syndromes, aplastic anemia, Diamond-Blackfan anemia, myelofibrosis, paroxysmal nocturnal hemoglobinuria, osteopetrosis and dyskeratosis congenita. The stem cell source was BM in ten patients and UCB in three. We retrospectively examined the conditioning regimens, stem cell source and dose, days to engraftment, survival and complication rate to see whether there was a significant advantage in using one source over the other. The median time to an absolute neutrophil count > 500 per microL was 25 days for UCB patients and 16 days for BM patients. The median time to a platelet count > 20,000 per microL was 55 days for UCB patients and 22 days for BM patients. The 100-day mortality was 66% in UCB patients and 20% in BM patients. The overall mortality rates were 66% and 40%, respectively. Three patients died prior to engraftment. Seven patients (54%) were still alive as of May 1999 with a median follow-up of 1574 days post-transplant. The patients transplanted with BM had faster engraftment and lower rates of graft-versus-host disease, 100-day mortality and overall mortality. HLA-matched sibling BM is preferred as a source but transplantation using unrelated UCB is still an option in treating pediatric bone marrow failure syndromes.
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PMID:Hematopoietic stem-cell transplantation using unrelated cord-blood versus matched sibling marrow in pediatric bone marrow failure syndrome: one center's experience. 1056 77

Mutations in the human telomerase RNA (TERC) occur in autosomal dominant dyskeratosis congenita (DKC). Because of the possibility that TERC mutations might underlie seemingly acquired forms of bone marrow failure, we examined blood samples from a large number of patients with aplastic anemia (AA), paroxysmal nocturnal hemoglobinuria (PNH), and myelodysplasia (MDS). Only 3 of 210 cases showed heterozygous TERC mutations: both nucleotide 305 (n305) (G>A) and n322 (G>A) were within the conserved region (CR) 4-CR5 domain; n450 (G>A) was localized to the boxH/ACA domain. However, only one patient (with a mutation at n305 [G>A]) had clinical characteristics suggesting DKC; her blood cells contained short telomeres and her sister also suffered from bone marrow failure. Another 21 patients with short telomeres did not show TERC mutations. Our results suggest that cryptic DKC, at least secondary to mutations in the TERC gene, is an improbable diagnosis in patients with otherwise typical AA, PNH, and MDS.
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PMID:Mutations of the human telomerase RNA gene (TERC) in aplastic anemia and myelodysplastic syndrome. 1267 74

There have been many recent advances in our understanding of the molecular basis of neutropenia disorders, primarily through advances in genetic analysis of inherited disorders. Molecular and cellular studies now suggest that accelerated apoptosis of neutrophil precursors in the bone marrow is the common pathophysiologic mechanism. Severe congenital neutropenia and cyclic neutropenia, both usually inherited as autosomal-dominant disorders, are caused by mutations in the neutrophil elastase gene. Myelokathexis is attributed to the downregulation of the bcl-x protein, but the genetic basis is not yet known. The genes for several diseases with more complex phenotypes (eg, glycogen storage disease type 1b, Chediak-Higashi syndrome, Shwachman-Diamond syndrome, dyskeratosis congenita, Griscelli syndrome, Barth syndrome, and Wiskott-Aldrich syndrome) have all been identified recently. The molecular mechanisms for most acquired disorders causing neutropenia (eg, idiopathic neutropenia, pure white-cell aplasia, myelodysplasia, and aplastic anemia) are not yet known. Granulocyte colony stimulating factor (G-CSF) is effective treatment for several of these conditions. Through better understanding of these disorders, we anticipate that better treatments will be found in the future.
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PMID:Molecular basis and therapy of disorders associated with chronic neutropenia. 1290 73

Profound cytopenia involving all blood lineages, a hallmark of aplastic anemia (AA), can result in devastating morbidity and high mortality. Although various etiologies and distinct pathophysiologic mechanisms may be involved, a profound defect in the stem cell compartment is a unifying feature in most patients with AA. As a stem cell disease, AA is very instructive and provides insights into the function and quantity of normal hematopoietic stem cells and their ability to regenerate. Pathophysiologically, understanding of AA may reveal mechanisms as to the evolution of other related bone marrow failure syndromes such as paroxysmal nocturnal hemoglobinuria and myelodysplasia-clonal diseases of hematopoiesis associated with defective stem cells. Conversely, constitutional forms of AA occurring in association with Fanconi anemia and dyskeratosis congenita demonstrate the role of specific genes and pathways in the dysfunction of the stem cells leading to the failure of the stem cell compartment. The acquired mechanisms resulting in depletion of stem cells in AA may involve fundamental pathways such as apoptosis and senescence as well as exhaustion of proliferative capacity or excessive differentiation. Inherent in the paucity of the bone marrow in AA, the study of the stem cells in AA has been very difficult due to their natural rarity and disease-specific contraction of the stem cell pool. Despite these scientific challenges, laboratory studies and systematic clinical observation provide valuable information of significance beyond its specific application to AA.
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PMID:Hematopoietic stem cells in aplastic anemia. 1473 92

Telomeres represent the nucleoprotein tails of chromosomes that get shortened with each cell division. When the telomere length reaches a critical point, cell senescence and death occur. Telomerase is a reverse transcriptase that counteracts telomere loss by adding telomeric sequences. In patients with acquired aplastic anemia, the mean telomere length (TRF) of peripheral blood leukocytes is generally short when compared to normal controls, without it being clear whether a relationship between TRF and disease severity exists. Additionally, increased telomerase activity (TA) is found in the bone marrow mononuclear cell population (MNCs) of aplastic anemia patients, especially in the chronic form of the disease. Fanconi anemia (FA) patients generally demonstrate increased TA and short telomeres in peripheral blood MNCs, a fact attributed to the high turnover of hematopoietic progenitor cells in combination with direct breakages at telomeric sequences. Furthermore, a strong correlation has been shown between TRF and the severity of aplastic anemia, but not with FA evolution towards myelodysplastic syndrome or acute myeloblastic leukemia. In respect of dyskeratosis congenita (DC), a disease of either X-linked or autosomal dominant/recessive inheritance which is characterized by premature ageing of highly regenerative tissues, studies have been carried out in order to elucidate whether the X-linked DC is caused by a defect in ribosomal RNA processing and/or telomere maintenance. Finally, the direct genetic link established between DC pathogenesis and short telomeres may lead to the development of new therapeutic protocols for diseases characterized by short telomere length and subsequent genomic instability.
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PMID:Telomere length variation and telomerase activity expression in patients with congenital and acquired aplastic anemia. 1503 32

New discoveries in cell biology, molecular biology and genetics have unveiled some of the pathophysiological mysteries of some of the bone marrow failure syndromes. Many of these discoveries have revealed why these syndromes show so much clinical overlap and some hold the potential for influencing the development of new therapies. In children and adults with pancytopenia and hypoplastic bone marrows proper differential diagnosis requires that some attention be directed toward defining molecular and cellular pathogenetic mechanisms because, once identified, some of these mechanisms will clearly suggest rational therapeutic approaches, treatment options that should be avoided, or both. In Section I, Drs. Jeffrey Lipton and Grover Bagby review the approach to diagnosis and management of patients with the inherited bone marrow failure syndromes, Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, and the Shwachman-Diamond syndrome. Extraordinary progress has been made in identifying the genes bearing pathogenetically relevant mutations in these disorders, but slower progress has been made in defining the precise functions of the proteins these genes encode in normal cells, in part because it is increasingly obvious that the proteins are multifunctional. In practice, it is clear that in patients with dyskeratosis congenita and Fanconi anemia, the diagnosis must be considered not only in children but in adults as well. In Section II, Dr. Elaine Sloand outlines a very practical and evidence-based approach to diagnosis and management of acquired hypoplastic states emphasizing overlap between non-clonal and clonal hematopoiesis is such conditions. The pathogenesis of T lymphocyte-mediated marrow failure is presented as a clear-cut rationale for use of immunosuppressive therapy and stem cell transplantation. Practical management of patients with refractory disease with and without evidence of clonal evolution (either paroxysmal nocturnal hemoglobinuria [PNH] or myelodysplasia [MDS]) is presented. In Section III, the challenge of hypoplastic MDS is reviewed by Dr. Charles Schiffer. After reviewing the most up-to-date classification scheme, therapeutic options are reviewed, focusing largely on agents that have most recently shown some promising activity, including DNA demethylating agents, thalidomide and CC5013, arsenic trioxide, and immunosuppressive therapy. Here are also outlined the rationale and the indications for choosing allogeneic bone marrow transplantation, the only therapy with known curative potential.
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PMID:Marrow failure. 1556 90

Human telomerase has two core components, the RNA molecule (TERC) that provides the template for telomere repeat elongation and a reverse transcriptase (TERT) that is responsible for the addition of telomere repeats at the ends of each chromosome. Mutations in TERC have been found in the autosomal-dominant form of the inherited bone marrow failure syndrome dyskeratosis congenita and in a subset of patients with aplastic anemia and myelodysplasia. These patients have short telomeres compared to age-matched controls. These observations suggest that uncharacterised cases of dyskeratosis congenita/aplastic anemia may have mutations in TERT or other molecules that associate with TERC in the telomerase complex. We have therefore screened the TERT gene for mutation by denaturing HPLC in 80 patients with inherited and acquired bone marrow failure (24 with dyskeratosis congenita, 36 with constitutional aplastic anemia, 13 with idiopathic aplastic anemia and 7 with other forms of bone marrow failure). 15 different TERT mutations have been identified. Of these, 5 are in flanking intron sequences, 6 are synonymous and 4 are non-synonymous (missense) substitutions in the coding sequence. These are the first natural mutations of TERT to be described and we highlight their possible pathogenic role in the development of bone marrow failure.
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PMID:Mutations in the reverse transcriptase component of telomerase (TERT) in patients with bone marrow failure. 1693 4

Myelodysplastic syndrome (MDS), considered a pre-leukemic state, has recently been categorized as a subset of bone marrow failure syndromes. Unlike other subtypes of bone marrow failure syndromes, such as aplastic anemia or dyskeratosis congenita, little is known about genetic alterations of human telomerase in MDS, despite the fact that immune cells from patients with MDS frequently exhibit telomere attrition.
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PMID:Lack of mutations of the human telomerase RNA gene (hTERC) in myelodysplastic syndrome. 1592 88

Mutations in the human telomerase RNA gene (TERC) cause autosomal dominant dyskeratosis congenita and have been detected in individuals with bone marrow failure. Here, we screened for TERC mutations in a cohort of 80 children with hypocellular myelodysplastic syndrome and detected TERC alterations in two of them.
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PMID:TERC mutations in children with refractory cytopenia. 1667 76


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