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| Alpha Thalassemia States Heterozygous states of alpha thalassemia express themselves as silent carrier (one loci deleted) thalassemia minor (two loci deleted) hemoglobin H disease (three loci deleted) The homozygous state (all four loci deleted), alpha thalassemia major, is incompatible with life. | View Page |
| Defining Alpha Thalassemia Alpha thalassemia demonstrates problems with alpha globin chain production. One to four loci that code for the alpha chain may be deleted from chromosome 16. 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 alpha genes. This unit of study deals only with the forms of alpha thalassemia that have entire loci deleted. | View Page |
| Alpha Thalassemia Major Gene deletions that cause alpha thalassemia can be homozygous or heterozygous deletions. Homozygous alpha thalassemia (alpha thalassemia major), also known as hydrops fetalis, is a lethal hemoglobin disorder which usually results in stillborn infants. Both alpha chain loci on each chromosome of the pair are deleted, resulting in a total absence of alpha chains. These chains are needed for all normal hemoglobins. If born live, infants with alpha thalassemia major exhibit hepatosplenomegaly, ascites, edema, low birth weight and die within a few hours. Ethnic groups most commonly associated with this form of alpha thalassemia include primarily Southeast Asians and sometimes people of the islands in the Mediterranean. | View Page |
| Chromosome 16 Alpha Thalassemia Silent Carrier In the Silent Carrier (-/), only one loci is deleted or inactive. Hemoglobin A is still able to be made to its fullest amount, 97-98%.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 16 Alpha thalassemia Minor In alpha thalassemia minor, two loci are deleted or inactive. Either homozygous or heterozygous states are possible. | View Page |
| Chromosome 16 Alpha Thalassemia Intermedia When three loci of alpha chains are deleted (--/-) or inactive, only 70-90% of Hemoglobin A is made. The excess beta chains that remain unpaired form the tetramers of Hemoglobin H.(drawing modified from Harmening, 1999) | View Page |
| Alpha Thalassemia Minor - Heterozygous In the heterozygous state (--/), one parent contributes a normal gene while the other one a gene with both alpha chain loci deleted.(drawing modified from Harmening, 1999) | View Page |
| 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 |
| Thalassemia results from which of the following? | View Page |
| Chromosome 11 Beta Thalassemia Minor B+/B In Beta thalassemia minor B+/B, one beta gene locus is partially deleted or inactive. With this deletion, only 85% to 95% of the normal level of Hb A is made.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Minor B0/B In Beta thalassemia minor, B0/B, one beta gene locus is completely deleted or inactive.Hemoglobin A production is down to 70% - 85% in this state of beta thalassemia.(drawing modified from Harmening, 1999) | View Page |
| Chromosome 11 Beta Thalassemia Intermedia B0/B+s In Beta thalassemia intermedia B0/B+s, there is one completely deleted or inactive beta chain gene, while the other is partially deleted or inactive.This state also results in Hb A production of 55%-75% of normal.(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 |