Transient myeloproliferative disease | |
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Other names | Transient abnormal myelopoiesis (TAM), transient leukemia, myeloid leukemia of Down syndrome |
Transient myeloproliferative disease (TMD) occurs in a significant percentage of individuals born with the congenital genetic disorder, Down syndrome. It may occur in individuals who are not diagnosed with the syndrome but have some hematological cells containing genetic abnormalities that are similar to those found in Down syndrome. TMD usually develops in utero, is diagnosed prenatally or within ~3 months of birth, and thereafter resolves rapidly and spontaneously. However, during the prenatal-to-postnatal period, the disease may cause irreparable damage to various organs and in ~20% of individuals death. Moreover, ~10% of individuals diagnosed with TMD develop acute megakaryoblastic leukemia at some time during the 5 years following its resolution. TMD is a life-threatening, precancerous condition in fetuses [1] as well as infants in their first few months of life. [2]
Transient myeloproliferative disease involves the excessive proliferation of non-malignant megakaryoblasts. Megakaryoblasts are hematological precursor cells which mature to megakaryocytes. Megakaryocytes release platelets into the bloodstream. Platelets are critical for normal blood clotting. [3] In consequence of this mutation, megkaryoblasts fail to mature properly, accumulate in multiple organs, may damage these organs, and may become cancerous. The diseases also causes a reduction in the maturation of erythroblasts to circulating red blood cells and, consequently, mild anemia. [4]
Most individuals with TMD have clinical evidence of damage to various organs, particularly the liver, due to megakaryoblast infiltration, the accumulation of fluid in various tissue compartments, a bleeding tendency due to low levels of circulating platelets (i.e. thrombocytopenia), anemia due to reduced production of red blood cells, and/or other signs or symptoms of the disorder. [5] However, some individuals with transient myeloproliferative disease have a presumably small clone of rapidly proliferating megakaryoblasts with inactivating GATA1 mutations but no other signs or symptoms of the disease. This form of TMD is termed silent transient abnormal myelopoiesis (i.e. silent TAM). Silent TAM is of clinical significance because it, like symptomatic TMD, may progress to an acute megakaryoblastic leukemia. This progression occurs in ~10% of TMD cases at some time during the 4-5 following birth and is due to the acquisition by the rapidly proliferating megakaryoblast clones of oncogenic mutations in other genes. [2]
Chemotherapeutic regimens are used to treat individuals with TMD but only those who have life-threatening complications of the disease. It is not known if these regimens have an impact on the development of acute megakaryoblastic leukemia. Currently, it is recommended that individuals with TMD be followed medically for signs, symptoms, or laboratory evidence of its progression to this malignant disease with the notion that its early treatment may be of clinical benefit. [2]
Transient myeloproliferative disease develops and may be of concern in fetuses. Features in a review of 39 reported fetal cases include: reduced platelet production often accompanied by significantly reduced levels of circulating platelets; reduced red blood cell production sometimes accompanied by mild anemia; increased levels of circulating megakaryoblasts and white blood cells; grossly enlarged liver and liver dysfunction due to an excessive accumulation of platelet precursor cells; enlarged spleen presumed due mostly to the portal hypertension accompanying liver disease with extramedullary hematopoiesis possibly contributing to the enlargement; accumulation of excessive fluid in bodily compartments such as the pericardial, pleural, abdominal spaces; hydrops fetalis, i.e. the accumulation of excessive fluid in two or more bodily compartments; cardiomegaly and other cardiac abnormalities resulting form atrial septal defects, small ventricular septal defects, and/or, possibly, accumulation of megakaryocytes and secondary cardiac fibrosis. [1] Hydrops fetalis, when accompanied by liver dysfunction, is a particularly poor prognostic combination in TMD. [6]
Clinical features in a review of 3 studies reporting on a total of 329 cases of symptomatic TMD include: premature birth (33-47%); enlarged liver (55-62%); evidence of liver dysfunction (13-63%); enlarged spleen (36-44%); heart disease (47-71%); gastrointestinal abnormalities (1-25%); and fluid accumulations in lung, heart, and/or abdomen (16-21%). In other studies; 5% of cases were associated with a vesiculopapular eruption; 3-6% of cases were associated with kidney failure or insufficiency presumed due mostly to complications of cardiac and/or liver dysfunction; rare cases of lung dysfunction due primarily to its compression by a massively enlarged liver and/or fluid accumulations in the pleural space; [2] and rare cases of asymptomatic megakaryoblastic infiltration and secondary fibrosis in the pancreas. [5] Other reports find decreased levels circulating platelets in 50% of cases, abnormal blood clotting in 10-25% of cases, anemia in 5-10%, and increased levels of circulating white blood cells in 50% of cases. The incidence of all these features except for low levels of blood platelets are appreciably higher in TMD than in Down syndrome individuals that lack inactivating GATA1 mutations. [2] There are also uncommon instances of stillbirths and infant death within 24 hours of delivery. [1]
Silent TAM lacks almost all of the clinical features of TMD, i.e. newborns with this disease exhibit no signs or symptoms that differ from those found in Down syndrome individuals who lack inactivating GATA1 mutations. Silent TAM nonetheless carries the threat of progressing to AMKL with an incidence similar to that occurring in TMD. [2]
Down syndrome is caused be the presence of an extra chromosome 21 (i.e. trisomy 21) due to a failure in normal chromosomal pairing or premature unpairing during the cell division of meiosis in egg or sperm cells. In these cases, virtually all cells in Down syndrome individuals bear an extra chromosome 21. However, there are other genetic changes that may either cause Down syndrome or cause an individual without Down syndrome to bear disease susceptibilities of the syndrome. These genetic changes include: a) genetic mosaicism in which some body cells bear a normal chromosome complement while others bear an extra chromosome 21; b) a part of chromosome 21 is located on another chromosome due to a Robertsonian translocation; c) partial trisomy 21 in which only part of chromosome 21 is duplicated; d) an isochromosome in which chromosome 21 contains two long but no short arms; and e) key genes on chromosome 21 are duplicated on this or other chromosomes. [7] These genetic changes do occur in rare cases of individuals who do not have Down syndrome but nonetheless develop transient myeloproliferative disease [8] due to the presence of extra copies of key genes normally found on chromosome 21 genes caused by mosaic, Robertsonian translocation, partial trisomy 21, isochromosome formation, or duplication. [5]
Down syndrome by itself (i.e. in the absence of GATA1 gene mutations) is a cause for numerous hematological abnormalities which are similar to those seen in TMD. These Down syndrome-related abnormalities include increased numbers of stem cell precursors to platelets and red blood cells, impaired maturation of these precursors to platelets and red blood cells, thrombocytopenia, abnormal bleeding, anemia, leukocytosis, and serious liver damage. Since TMD is restricted to individuals with Down syndrome or otherwise have an excess of key chromosome 21 genes, it is suggested that certain chromosome 21 genes that are in triplicate and cause these hematological disorders in Down syndrome are essential for the development of GATA1 inactivating mutations and thereby TMD. These genes include ERG , a potentially cancer-causing oncogene that codes for a transcription factor; DYRK1A , which codes for a protein kinase type of enzyme involved in promoting cellular proliferation; and RUNX1 , which codes for a transcription factor that regulates the maturation of hematological stem cells and, when mutated, is involved in the development of various myeloid neoplasms. [2] It is hypothesized that trisomy 21 induces genome instability and stress, contributing to the development of somatic mutations associated with progression to leukemia. [9]
The human GATA1 gene is located on the short (i.e. "p") arm of the X chromosome [10] at position 11.23. [11] It is 7.74 kilobases in length, consists of 6 exons, and codes for a full length protein, GATA1, of 414 amino acids (atomic mass=50 kilodaltons) and a shorter protein, GATA1-S (also termed GATA1s). GATA1-S lacks the first 83 amino acids of GATA1 and consists of 331 amino acids (atomic mass = 40 kilodaltons). [12] GATA1 and GATA1-S are transcription factors, i.e. nuclear proteins that regulate the expression of genes. [10] The genes targeted by these two transcription factors help control the maturation of megakaryoblasts and promegakaryocytes to platelet-forming megakaryocytes [12] and the maturation of erythroblasts to red blood cells. [13] GATA1-S is less active than GATA1 in controlling most of these genes including those that stimulate megakaryoblast maturation but appears more effective than GATA1 in stimulating megakaryoblast proliferation. [12] Outside of the Down syndrome (or a triplication in key chromosome 21 genes), GATA1 inactivating mutations cause or contribute to various non-malignant X-linked bleeding and anemic disorders that are due to failures in the maturation of precursor cells to platelets and red blood cells. [4]
The GATA1 mutations in Down syndrome cause TMD. They occur in exon 2 or 3 of the gene and are truncating mutations that result in the gene's exclusive formation of GATA1-S, i.e. the gene makes no GATA1. [12] Some 20% of individuals with Down syndrome bear one truncating mutation although some may bear up to 5 different truncating mutations and therefore have 5 different GATA1 mutant clones. These mutations occur in utero and can be detected in fetuses of 21 weeks gestational age. In the absence of GATA1, the GATA1-S transcription factor increases the proliferation but not maturation of megakaryoblasts [4] and is insufficient to support the normal maturation of red blood cell precursors. [14] Consequently, fetuses [1] and, during their first few months of live, infants [2] with these mutations exhibit extensive accumulations of immature megakaryoblasts in fetal blood-forming organs (particularly liver and bone marrow) and decreases in circulating platelet counts; they may also exhibit modest reductions in circulating red blood cells; and they may exhibit severe injuries in various organs. In ~80% of individuals, hematological changes resolve completely within ~3 months although organ injuries, particularly those to the liver, may take months or even years to fully resolve. During this resolution period, GATA1 mutations become undetectable. However, the original mutations are again detected in the acute megakaryoblastic leukemia cells indicating that the GATA1 mutations causing TMD decrease to undetectable levels as TMD resolves but, at least in cases that progress to AMKL, persist in a tiny clone of megakaryoblasts that evolve into the malignant cells of AMKL. In most cases, this evolution occurs over 1–5 years but in ~20% of cases the in utero [1] or postnatal disease [3] is severe, prolonged, and/or fatal or progresses to AMKL without exhibiting a resolution phase.[ citation needed ]
The GATA1 gene also regulates the maturation of eosinophils and dendritic cells. Its impact on the former cell type may underlie the increase in circulating blood eosinophils in TMD. [13]
TMD may be followed within weeks to ~5 years by a subtype of myeloid leukemia, acute megakaryoblastic leukemia. AMKL is extremely rare in adults. The childhood disease is classified into two major subgroups based on its occurrence in individuals with or without Down syndrome. The disease in Down syndrome occurs in ~10% of individuals who previously had TMD. [15] During the interval between TMD and the onset of AMKL, individuals accumulate multiple somatic mutations in cells that bear an inactivating GATA1 mutation plus trisomy 21 (or the presence of extra chromosome 21 genes involved in the development of TMD). These mutations are thought to result from the uncontrolled proliferation of blast cells caused by the GATAT1 mutation in the presence of trisomy 21 (or the presence of extra chromosome 21 genes involved in the development of TMD) and to be responsible for progression of the transient disorder to AMKL. The mutations occur in one or more genes including: TP53, FLT3, ERG, DYRK1A, CHAF1B, HLCS, RUNX1, MIR125B2 (which is the gene for microRNA MiR125B2CTCF, [3] STAG2, RAD21, SMC3, SMC1A, NIPBL, SUZ12, PRC2, JAK1, JAK2, JAK3, MPL, KRAS, NRAS , and SH2B3. [15]
The development and progression of TMD result from collaborations between various genes: 1) during fetal development, an immature megakaryoblast which has extra copies of key genes located on chromosome 21 (e.g. ERG, DYKR1A, and/or RUNX1) acquires an inactivating mutation in GATA1 that causes it to make only GATA1-S; 2) this cell(s) grows into a genetically identical group, i.e. a clone, of non-malignant megakaryoblasts which proliferate excessively, fail to mature normally, and over-populate fetal blood-forming organisms, particularly the liver and bone marrow, thereby establishing TMD; 3) most cells in this clone are still genetically programmed to die during the ensuing fetal and early postnatal period thereby resolving TMD; 4) some cells in this GATA1-mutant clone escape the death program although their numbers are too low for detection by current methods; 5) in ~10% of TMD cases, the surviving cells from the GATA1 mutant clone undergo an evolution to cancer, i.e. they acquire mutations in other genes (see preceding section) which causes at least one of them to be malignant, immortal, and rapidly proliferating thereby founding a clone of megakaryoblasts that have the original GATA1 mutation, extra chromosome 21 genes, and one or more one of the newly acquired oncogenic gene mutations; and 6) the cells in this malignant clone infiltrate, accumulate in, and injure various organs and tissues thereby establishing AMKL. [2] [7] These stages in the development and progression of TMD may involve up to 5 different GATA1 gene mutations in different megakaryoblasts and therefore result in the evolution of up to 5 different GATA1-mutant clones, at least one of which may found the malignant clone involved in AMKL. [4]
The severity of transient myeloproliferative disease appears to depend on the size of the GATA1 mutant clone. It is likely, for example, that the lack of clinical features in silent TAM is a reflection of the small size of its mutant GATA1 clone. [2]
The liver of TMD-individuals accumulate abnormally high numbers of platelet and -to a lesser extent- red blood cell precursors. The liver, it is suggested, may be the primary site for excessive proliferation of the GATA1 mutant clone(s) of platelet precursor cells, primarily megakaryobllasts and the accumulation of these precursor cells along to red blood cell precursor cells appears to be an important cause of the liver enlargement and dysfunction occurring in TMD. [15]
TMD is associated with fibrosis (i.e. replacement of normal tissue with fibrous tissue) in the liver. This fibrosis may be severe and even life-threatening. [16] Based primarily on mouse [17] and isolated human cell studies, [18] this myelofibrosis is thought to result from the excessive accumulation of mutant GATA1-bearing platelet precursor cells in these organs: the precursor cells make and release abnormally large amounts of cytokines (platelet-derived growth factor; transforming growth factor beta 1) which stimulate tissue stromal cells to become fiber-secreting fibroblasts.
ML-DS (Myeloid leukemia in Down syndrome) features mutations in the cohesin complex, including RAD21, STAG1, SMC3, SMC1A, and the associated factor NIPBL in over half of cases, whereas these mutations are rare in TAM (transient abnormal myelopoiesis). Notably, cohesin mutations alter chromatin accessibility at ERG, RUNX1, and GATA transcription factor motifs. [19]
Fetuses [1] and newborns [2] with Down syndrome without GATA1 inactivating mutations have numerous hematological abnormalities some of which are similar to those in TMD including increased numbers of circulating blasts, decreased numbers of circulating platelets and red blood cells, and increased numbers of circulating white blood cells. Also like TMD, these Down syndrome (no GATA1 mutation) individuals exhibit hepatomegaly, abnormal liver function tests, and jaundice. However, these abnormalities are usually more frequent and/or severe in TMD. Furthermore, enlarged spleen, fluid accumulations in body cavities, and leukemia cutis (i.e. a rash due to the infiltration of platelet precursor cells into the skin) occur in ~30, 9, and 5%, respectively, of TMD cases but are rarely observed in individuals with Down syndrome (no GATA1 mutation). The blood of individuals with TMD may contain grossly malformed blast cells, giant platelets, and fragments of megakaryocytes which are rarely seen in individuals with Down syndrome (no GATA1 mutation). Bone marrow examination reveals increases in blast cells in essentially all cases of TMED, increased fibrosis in a small but significant percentage of cases, defective maturation of platelet precursors in ~75% of cases, and defective maturation of red blood cell precursors in 25% of cases. These abnormalities are generally more extreme that those seen in Down syndrome (no GATA1 mutation). The overall constellation of abnormalities found in TMD often suggest its diagnosis. [5]
In all individuals suspected of having the symptomatic or silent disease, the diagnosis of TMD requires demonstrating the presence, in the platelet precursor cells of blood, bone marrow, or liver, of GATA1 mutations that are projected to cause the gene to make GATA1-S but not GATA1 transcription factors. Since these mutations are limited to a clone(s) of platelet precursor cells which may represent only a small fraction of all platelet precursor cells, high-throughput DNA sequencing methods are required to detect many cases of the disease, particularly in silent TAM cases which may have only a small number of platelet precursors with the mutation. [2] The in utero diagnosis of fetal TMD depends on medical ultrasound scanning to detect fluid accumulations in body cavities, cardiac abnormalities (particularly atrial septal defects), organ enlargements (particularly of the liver, spleen, or heart), fetal size, and fetal movements. Blood samples are obtained from the fetal umbilical cord to determine blood cell counts, measure blood enzymes to evaluate liver function, and the presence in circulating platelet precursor cells of GATA1 mutations that are associated with TMD. [1]
Since 80 to 90% of newborns with transient myeloproliferative disease recover within ~3 months (organ enlargement make take longer to resolve), treatment is generally restricted to cases with life-threatening complications. These complications include severe: a) hydrops fetalis; b) increases in circulating white blood cells (e.g. >10-fold elevations) that can lead to a blood disorder termed the hyperviscosity syndrome; c) bleeding due to disseminated intravascular coagulation or, less commonly, reduced levels of circulating platelet; d) liver dysfunction; or e) cardiac dysfunction. There have been no large controlled studies published on treatment but several small studies report that low dose cytarabine, a chemotherapeutic drug, has beneficial effects in these cases. High dose cytarabine, however, has been found to be highly toxic in infants with TMD; it is recommended that these dosages be avoided in TMD. The goal of low dose cytarabine in TMD is to reduce the load but not eradicate platelet precursors in tissues and/or circulating megakaryoblasts or, in cases of extreme leukocytosis, white blood cells, particularly since none of these cells are malignant. [2] [5] There is insufficient data to indicate the value of therapy in prenatal cases. Supportive fetal therapy consisting of repeated in utero transfusion of packed red blood cells and platelet concentrates has been reported to reduce the proportion of circulating blast cell, reduce fluid accumulations in fetal cavities, and reduce the size of an enlarged liver; preterm induction of delivery has also been used in infants with fetal distress. However, further studies are required to determine the clinical usefulness of these and other interventions in prenatal TMD. The Cochrane Organization rated the quality of evidence for these fetal interventions as very low. [1]
Experts suggest that individuals with symptomatic or silent TMD be followed medically for signs and/or symptoms of the disease's progression to AMKL. This includes physical examinations to measure liver and spleen size as well as complete blood counts to measure the levels of circulating platelets, erythrocytes, white blood cells, and platelet precursor cells. Recommendations for the frequency of these measurements vary from every 3 to 12 months. [2] A complex drug regimen that includes high dose cytarabine [20] has shown good results in treating AMKL. [2]
Overall mortality during the first year as reported in three studies (all of which included individuals treated for their TMD), range between 15 and 21% in TMD and between 4 and 12% in Down syndrome (no GATA1 mutation). Virtually all of the deaths occurring in TMD happened within the first 6 months. Risk factors that increased mortality in TMD were prematurity, extremely elevated circulating blast and/or white blood cells, hepatic dysfunction, ascites (i.e. fluid in the abdominal cavity), excessive bleeding and/or blood clotting, and kidney dysfunction. [5] About 10% of all TMD cases, including those with silent disease, will progress to AMKL at some time during the first 5 years after birth. AMKL associated with Down syndrome is far less severe a disease that AMKL not associated with the syndrome. Event free survival and overall survival (studies include chemotherapy-treated cases) during the 5 years following its diagnosis in Down syndrome children with AMKL is ~80%; it is 43% and 49%, respectively, in children with AMKL who do not have Down syndrome. Median survival in adult AMKL is only 10.4 months. [4]
TMD was first described and termed congenial leukemia by Bernard and colleagues in a 1951 publication. [21] It was defined to be limited to individuals with Down Syndrome and to be spontaneously regressing in 1954, [22] and thereafter reported to progress to a leukemia in two reports, the first published in 1957 [23] and the second published in 1964. [24] Respective reports by D. Lewis in 1981 [25] and Bennett et al in 1985 [26] indicated that the blast cells involved in TMD and its leukemic sequel were platelet precursor cells. Studies by J.D. Crispino and colleagues in 2002 [27] and 2003 [28] showed that GATA1 mutations were respectively involved in TMD and AMKL.
Leukemia is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called blasts or leukemia cells. Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections. These symptoms occur due to a lack of normal blood cells. Diagnosis is typically made by blood tests or bone marrow biopsy.
A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may include fatigue, shortness of breath, bleeding disorders, anemia, or frequent infections. Some types may develop into acute myeloid leukemia.
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 5×108/L (500/μL). Hypereosinophilia is an elevation in an individual's circulating blood eosinophil count above 1.5 × 109/L (i.e. 1,500/μL). The hypereosinophilic syndrome is a sustained elevation in this count above 1.5 × 109/L (i.e. 1,500/μL) that is also associated with evidence of eosinophil-based tissue injury.
Polycythemia is a laboratory finding in which the hematocrit and/or hemoglobin concentration are increased in the blood. Polycythemia is sometimes called erythrocytosis, and there is significant overlap in the two findings, but the terms are not the same: polycythemia describes any increase in hematocrit and/or hemoglobin, while erythrocytosis describes an increase specifically in the number of red blood cells in the blood.
Tumors of the hematopoietic and lymphoid tissues or tumours of the haematopoietic and lymphoid tissues are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making aplasia, myeloproliferation and lymphoproliferation closely related and often overlapping problems. While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of hematological malignancies. Hematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "hematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions. Not all hematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.
Primary myelofibrosis (PMF) is a rare bone marrow blood cancer. It is classified by the World Health Organization (WHO) as a type of myeloproliferative neoplasm, a group of cancers in which there is activation and growth of mutated cells in the bone marrow. This is most often associated with a somatic mutation in the JAK2, CALR, or MPL genes. In PMF, the bony aspects of bone marrow are remodeled in a process called osteosclerosis; in addition, fibroblast secrete collagen and reticulin proteins that are collectively referred to as (fibrosis). These two pathological processes compromise the normal function of bone marrow resulting in decreased production of blood cells such as erythrocytes, granulocytes and megakaryocytes, the latter cells responsible for the production of platelets.
Myeloproliferative neoplasms (MPNs) are a group of rare blood cancers in which excess red blood cells, white blood cells or platelets are produced in the bone marrow. Myelo refers to the bone marrow, proliferative describes the rapid growth of blood cells and neoplasm describes that growth as abnormal and uncontrolled.
Diamond–Blackfan anemia (DBA) is a congenital erythroid aplasia that usually presents in infancy. DBA causes low red blood cell counts (anemia), without substantially affecting the other blood components, which are usually normal. This is in contrast to Shwachman–Bodian–Diamond syndrome, in which the bone marrow defect results primarily in neutropenia, and Fanconi anemia, where all cell lines are affected resulting in pancytopenia. There is a risk to develop acute myelogenous leukemia (AML) and certain other cancers.
GATA-binding factor 1 or GATA-1 is the founding member of the GATA family of transcription factors. This protein is widely expressed throughout vertebrate species. In humans and mice, it is encoded by the GATA1 and Gata1 genes, respectively. These genes are located on the X chromosome in both species.
Chronic myelomonocytic leukemia (CMML) is a type of leukemia, which are cancers of the blood-forming cells of the bone marrow. In adults, blood cells are formed in the bone marrow, by a process that is known as haematopoiesis. In CMML, there are increased numbers of monocytes and immature blood cells (blasts) in the peripheral blood and bone marrow, as well as abnormal looking cells (dysplasia) in at least one type of blood cell.
Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative neoplasm that features a persistent neutrophilia in peripheral blood, myeloid hyperplasia in bone marrow, hepatosplenomegaly, and the absence of the Philadelphia chromosome or a BCR/ABL fusion gene.
ETV6 protein is a transcription factor that in humans is encoded by the ETV6 gene. The ETV6 protein regulates the development and growth of diverse cell types, particularly those of hematological tissues. However, its gene, ETV6 frequently suffers various mutations that lead to an array of potentially lethal cancers, i.e., ETV6 is a clinically significant proto-oncogene in that it can fuse with other genes to drive the development and/or progression of certain cancers. However, ETV6 is also an anti-oncogene or tumor suppressor gene in that mutations in it that encode for a truncated and therefore inactive protein are also associated with certain types of cancers.
Platelet-derived growth factor receptor beta is a protein that in humans is encoded by the PDGFRB gene. Mutations in PDGFRB are mainly associated with the clonal eosinophilia class of malignancies.
Factor interacting with PAPOLA and CPSF1 is a protein that in humans is encoded by the FIP1L1 gene. A medically important aspect of the FIP1L1 gene is its fusion with other genes to form fusion genes which cause clonal hypereosinophilia and leukemic diseases in humans.
Acute megakaryoblastic leukemia (AMKL) is life-threatening leukemia in which malignant megakaryoblasts proliferate abnormally and injure various tissues. Megakaryoblasts are the most immature precursor cells in a platelet-forming lineage; they mature to promegakaryocytes and, ultimately, megakaryocytes which cells shed membrane-enclosed particles, i.e. platelets, into the circulation. Platelets are critical for the normal clotting of blood. While malignant megakaryoblasts usually are the predominant proliferating and tissue-damaging cells, their similarly malignant descendants, promegakaryocytes and megakaryocytes, are variable contributors to the malignancy.
Hematologic diseases are disorders which primarily affect the blood and blood-forming organs. Hematologic diseases include rare genetic disorders, anemia, HIV, sickle cell disease and complications from chemotherapy or transfusions.
Myeloid leukemia is a type of leukemia affecting myeloid tissue.
Clonal hypereosinophilia, also termed primary hypereosinophilia or clonal eosinophilia, is a grouping of hematological disorders all of which are characterized by the development and growth of a pre-malignant or malignant population of eosinophils, a type of white blood cell that occupies the bone marrow, blood, and other tissues. This population consists of a clone of eosinophils, i.e. a group of genetically identical eosinophils derived from a sufficiently mutated ancestor cell.
The Emberger syndrome is a rare, autosomal dominant, genetic disorder caused by familial or sporadic inactivating mutations in one of the two parental GATA2 genes. The mutation results in a haploinsufficiency in the levels of the gene's product, the GATA2 transcription factor. This transcription factor is critical for the embryonic development, maintenance, and functionality of blood-forming, lympathic-forming, and other tissues. The syndrome includes as its primary symptoms: serious abnormalities of the blood such as the myelodysplastic syndrome and acute myeloid leukemia; lymphedema of the lower limbs, and sensorineural hearing loss. However, the anomalies caused by GATA2 mutations are highly variable with some individuals showing little or no such symptoms even in old age while others exhibit non-malignant types of hematological anomalies; lymphedema in areas besides the lower limbs, little or no hearing loss; or anomalies in other tissues. The syndrome may present with relatively benign signs and/or symptoms and then progress rapidly or slowly to the myelodysplastic syndrome and/or acute myeloid leukemia. Alternatively, it may present with one of the latter two life-threatening disorders.
GATA2 deficiency is a grouping of several disorders caused by common defect, namely, familial or sporadic inactivating mutations in one of the two parental GATA2 genes. Being the gene haploinsufficient, mutations that cause a reduction in the cellular levels of the gene's product, GATA2, are autosomal dominant. The GATA2 protein is a transcription factor critical for the embryonic development, maintenance, and functionality of blood-forming, lymphatic-forming, and other tissue-forming stem cells. In consequence of these mutations, cellular levels of GATA2 are deficient and individuals develop over time hematological, immunological, lymphatic, or other presentations that may begin as apparently benign abnormalities but commonly progress to severe organ failure, opportunistic infections, virus infection-induced cancers, the myelodysplastic syndrome, and/or leukemia. GATA2 deficiency is a life-threatening and precancerous condition.