Genes and ALLGGenes and ALLGenes and ALLEnglishOncologyChild (0-12 years);Teen (13-18 years)BodySkeletal systemConditions and diseasesAdult (19+)NA2018-03-06T05:00:00Z9.8000000000000050.0000000000000515.000000000000Flat ContentHealth A-Z<p> Learn how gene changes can cause acute lymphoblastic leukemia (ALL).</p><p>Acute lymphoblastic leukemia (ALL) can develop because of gene changes inside leukemic stem cells. These changes can include chromosome translocations or changes in the number of chromosomes.</p><h2> Key points </h2> <ul><li>Chromosome translocations or a change in the number of chromosomes will often occur in a child with ALL's leukemic cells.</li></ul>
Gènes et LLAGGènes et LLAGenes and ALLFrenchOncologyChild (0-12 years);Teen (13-18 years)BodySkeletal systemConditions and diseasesAdult (19+)NA2018-03-06T05:00:00ZFlat ContentHealth A-Z<p>Apprenez comment les changements génétiques peuvent provoquer une leucémie lymphoblastique aiguë (LLA).</p><p>La leucémie lymphoblastique aiguë (LLA) se développe à cause de mutations génétiques dans les cellules souches leucémiques. Il peut s’agir de translocations ou de changements dans le nombre de chromosomes.</p><h2>À retenir</h2> <ul><li>Les translocations de chromosomes ou une modification du nombre de chromosomes se produiront souvent chez un enfant présentant des cellules leucémiques de la LLA.</li></ul>

 

 

 

 

Genes and ALL2828.00000000000Genes and ALLGenes and ALLGEnglishOncologyChild (0-12 years);Teen (13-18 years)BodySkeletal systemConditions and diseasesAdult (19+)NA2018-03-06T05:00:00Z9.8000000000000050.0000000000000515.000000000000Flat ContentHealth A-Z<p> Learn how gene changes can cause acute lymphoblastic leukemia (ALL).</p><p>Acute lymphoblastic leukemia (ALL) can develop because of gene changes inside leukemic stem cells. These changes can include chromosome translocations or changes in the number of chromosomes.</p><h2> Key points </h2> <ul><li>Chromosome translocations or a change in the number of chromosomes will often occur in a child with ALL's leukemic cells.</li></ul><h2>Chromosome translocations</h2><p>Inside leukemic cells, a part of a chromosome can separate itself and attach to other unrelated chromosomes, producing new chromosomes that express genes in different ways. When chromosomes spontaneously rearrange themselves this way, it is called a translocation.</p> <figure> <span class="asset-image-title">Chromosomal Translocation</span><img src="http://assets.aboutkidshealth.ca/akhassets/Chromosomal_translocation_MED_ILL_EN.jpg" alt="Normal chromosomes and chromosomes with translocation" /> </figure> <p>Problems arise when the translocation produces a new gene that instructs the cell to do things it normally would not — for instance, tell the cell to divide uncontrollably. For ALL, many translocations are more commonly found in different age groups. In a healthy cell, there are normally 46 copies of chromosomes; two copies of each. Every pair is numbered 1 through 23. </p><p>Translocation of chromosome 4 and 11 typically occurs in up to 80% of ALL cases of infants younger than one year old. The gene that is involved in this translocation is called the MLL gene. This is a subtype of ALL called Infant ALL.</p><p>The most frequent translocation that occurs inside leukemic cells in children 2–9 years of age is when parts of chromosome 12 and 21 fuse together. This is called ETV6-RUNX1 fusion (previously known as TEL-AML1). This translocation represents about 20% to 25% of all childhood ALL cases and is associated with precursor B-cell ALL, which is when there are too many B-cell lymphoblasts (immature white blood cells) in the blood and bone marrow. </p><p>The presence of this translocation is generally associated with a more favorable prognosis.</p><p>It is possible to find leukemic cells with chromosome 9 and 22 translocated. This is also called a Philadelphia (Ph)-chromosome-positive ALL and represents from 3% to 5% of childhood ALL. It is more common in children older than 10 years with precursor B-cell ALL. Special medications treat this type of ALL, which is considered high-risk. </p><p>Several other translocations may be present in your child’s leukemia. These should be discussed with your child's oncologist.</p><h2>Changes in the number of chromosomes</h2><p>Some leukemic cells have too few or too many chromosomes.</p><h3>Too many chromosomes</h3><p>About 20% to 25% of children with precursor-B ALL have more than 50 copies of chromosomes per cell. Typically, there are more copies of chromosomes 4, 10 and 17 inside the leukemic cell. A cell that has too many copies of chromosomes is called hyperdiploid. Children with hyperdiploid cancer cells generally have a good prognosis, as they respond very well to chemotherapy.</p><h3>Too few chromosomes</h3><p>In approximately 5% of cases, leukemic cells have too few chromosomes. A cell that has less than 44 copies is called hypodiploid cell. The prognosis is not as optimistic as in hyperdiploid.</p><p>In very few cases of ALL, leukemic cells can be "near-haploid," which means they have 24–29 copies of chromosomes. Although this indicates a very poor prognosis, it is very, very rare.</p>Genes and ALLFalse