Delta-beta Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Delta-beta and links to relevant pages within the course.
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| Defining Beta Thalassemia Beta thalassemia demonstrates problems with beta globin chain production. One or two loci that code for the beta chain may be deleted from chromosome 11. The greater the number of loci deleted or inactivated, the greater the severity of the anemia which develops. Many different mutations exist that result from partial deletions of beta genes. This unit of study deals only with the forms of beta thalassemia that have entire loci deleted. Deletions of additional globin genes coded for on chromosome 11 can result in such combinations as delta-beta thalassemia. | View Page |
| Beta Thalassemia States Heterozygous states can express themselves as beta thalassemia minor, beta thalassemia intermedia, and silent carrier. The homozygous state is beta thalassemia major, though one type of beta thalassemia intermedia is caused by a homozygous state. A larger deletion on chromosome 11 results in delta-beta thalassemia, which also has heterozygous and homozygous states. | View Page |
| Delta-Beta Thalassemia Delta-beta thalassemia exists in both heterozygous and homozygous forms. The symptoms are mild to moderate depending on the severity of the disease.This form of beta thalassemia can be found in many ethnic groups, but is most common in persons from Greece and Italy. | View Page |
| Chromosome 11 Delta-Beta Thalassemia Minor Occasionally, the beta chain gene deletion extends to include the locus for the delta chain gene. If this deletion occurs on only one chromosome of the pair, it creates delta-beta thalassemia minor. Delta-Beta 0/ BetaHb A and A2 will both be decreased and Hb F will be increased.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Delta-Beta Thalassemia Intermedia Delta-beta thalassemia intermedia exists when both gene loci for beta and delta chains are deleted or inactive on one chromosome, while the other chromosome contains a beta chain gene that is partially deleted or inactive. Delta-Beta 0/ Beta+sIn this state the majority of hemoglobin will be Hb F, with very little Hb A and A2 present.(drawing modified from Harmening, 1999) | View Page |
| The diagram above represents which of the following beta thalassemias? | View Page |
| Chromosome 11 Delta-Beta Thalassemia Major Delta-beta thalassemia major, Delta-beta 0/ Delta-beta0, exists when both gene loci for beta and delta chains are completely deleted or inactive on both chromosomes. In this state, only Hb F can be made.(drawing modified from Harmening, 1999) | View Page |
| Hematologic Findings For Various Types of Beta Thalassemia Beta Thalassemia Silent Carrier Beta Thalassemia Minor Beta Thalassemia Intermedia Beta Thalassemia Major Delta-Beta Thalassemia Anemia Absent Mild to absent Moderate Severe Mild Red blood cell (RBC) count Normal Increased Decreased to normal Decreased Decreased to normal Hemoglobin(Hb) Normal Decreased to normal (10 - 12 g/dL) Decreased (7 - 10 g/dL) Marked decrease (<7 g/dL) Decreased to normal (8 - 13 g/dL) Mean corpuscular volume (MCV) Slight to no decrease Marked decrease Marked decrease Marked decrease May be slightly decreased Mean corpuscular hemoglobin concentration (MCHC) Slight to no decrease Marked decrease Marked decrease Marked decrease May be slightly decreased Red blood cell distribution width (RDW) Normal Normal to slightly increased Increased Increased Normal RBC morphology Normal Marked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not present Marked hypochromia and microcytosis Codocytes (target cells) Possible basophilic stippling Nucleated RBCs are usually not present Marked hypochromia and microcytosis Codocytes (target cells) schistocytes ovalocytes basophilic stippling polychromasia nucleated RBCs Possible hypochromia and microcytosis Codocytes (target cells) Basophilic stippling Reticulocyte count Normal May be slightly increased Slightly increased (<5%) Mildly increased (5 - 10%) Mildly increased Hb electrophoresis Normal pattern Decreased amount of Hb A Variable amounts of Hb A2 and Hb F Decreased amount of Hb A Variable amount of Hb A2 Hb F is usually increased Severly decreased amount of Hb A Variable amount of Hb A2 Usually an increased amount of Hb F Decreased amount of Hb A and Hb A2 Increased amount of Hb F (15 - 20%) If red blood cells are normochromic and normocytic, the RBC, Hb, and Hematocrit (HCT) test values follow in three-fold progression (i.e., RBC x 3 = Hb and Hb x 3 = HCT). This is sometimes referred to as "the rule of threes." This rule will usually not apply in cases of beta thalassemia, particularly beta thalassemia minor where the RBCs are not normochromic and are microcytic, and where there is a disproportionate number of RBCs for the amount of hemoglobin that is present. | View Page |
| Hemoglobin electrophoresis patterns in Beta thalassemia The following list corresponds to this image of an alkaline hemoglobin electrophoresis.Lanes 1 and 2: normal patient specimenHb A is over 98% with a small amount of Hb A2 visibleLanes 3 and 4: Beta thalassemia minorHb A is decreased to 94%, Hb A2 is increased at 5%, and Hb F is 1%Lanes 5 and 6: Delta-beta thalassemia majorNo Hb A or A2 is present, Hb F is 100%Lanes 7 & 8: Delta-beta thalassemia intermediaHb A is 8.5%, Hb A2 is 3.5% and Hb F is 88%Lane 9: AF control Lane 10: ASC control(Remember, AF and ASC are labels and do not indicate the order of migration.) | View Page |