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Thalassemia is best thought of as a group of disorders rather than a single disease. They demonstrate a hemoglobin synthesis disorder in which there exists a defect in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene.

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.

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)

Look at the phase in which reactions are occurring. Reactions at immediate spin (IS) usually are not clinically significant. Reactions at AHG are clinically significant. Check for a match in the reactivity pattern by comparing sample reactions and individual antibody reactions Varying strength of reactions could indicate dosage. Dosage means that there are two "doses" of the same antigen present on the red cells . Antibodies that exhibit dosage react more strongly with homozygous cells (e.g., Jka Jka ) than with heterozygous cells (e.g., Jka Jkb) .

In this example the patient's plasma tests positive with both screening cells at a strength of 4+. In the panel below, reaction patterns show varying strengths, 2+ to 4+ (highlighted in green).4+ could indicate one strong antibody or a combination of several antibodies that increases the strength of the reaction.3+ could indicate one strong antibody.2+ could indicate one the reaction between one weak antibody and the corresponding antigen that is present on with the other target antigen not present on that testing cell. If the panel cell is in the heterozygous state, the reaction of the antibodies present may be weaker if they commonly exhibit dosage. Since Cw, Kpa, Jsa, Lua are not present on the testing cells they are probably not causing these reactions. Perform rule outs using panel cells 5 and 7 (sample had no reaction in any phase with these panel cells) Cells that have at least 1 out of the 3 rule outs needed: C, c, e, K,k, Kpb, Jsb, Fya, Jkb, Lea, M, N, s, P1, Lub Antibodies that could not be ruled out with this panel: D,E, K, Fyb, Jka, Leb, S Predominant pattern of 4+ in panel cells 1,2,3,4,10 matches D Varying strengths in reactions indicates a possible second antibody so selected cells should be picked to aid in identification Find a panel cell negative for D (antibody you suspect) and homozygous positive for the antibody you are trying to rule out. For example: D E e K k Fya Fyb Jka Jkb Lea Leb S s Donor cell 1 0 0 + 0 + 0 + + + 0 + 0 + Donor cell 1 could be used as a rule out test for e, k, Fyb and Leb. Reactions should be negative if these antibodies are not present.You should have a total of 3 negative reactions with panel or screen cells to rule out potential antibodies. If reactions with this panel cell are negative, then e and k can be ruled out with a total of 3 to rule out reactions. Selected cells should be picked for each antibody that needs to be ruled out in order to determine the identity of the other antibody

Antibodies ruled out with 3 reactions: D, c, k, Kpb, Jsb, Leb, P1, and Lub (panel cells used for rule out are in green). Antibodies still needing selected cells for rule outs: C, Lea, E, M, Jkb, S, s (need 2 reactions)Fya,Jka, N, K (need 3 reactions)e, Fyb (needs 1 reaction) Jsa, Kpa, Cw, and Lua all need three reactions for rule-out but these are all low-frequency antigens. It is difficult to find panel cells with these antigens present to allow testing. They will fall in the "unable to rule out" category.Reactions are occurring in the AHG phase only and there is varying strengths of reactivity, which could indicate dosage and/or multiple antibodies.The pattern of reactivity closely matches Fya (cells 2,5,7,8,9 are positive). Of the remaining antibodies that have no rule-out reactions, anti-K is the possible second antibody (present on cell 2 and 10 and screen cell I). Explanation for the varying strengths in reactions: Panel cell 2: Fya (heterozygous) and K present so stronger reaction of 4+. Panel cell 5 and 8: Fya is heterozygous, so weaker reaction of 2+. Panel cell 7 and 9: Fya is homozygous, so stronger reaction of 3+. Panel cell 10: K is (homozygous, so stronger reaction of 3+.

Rule-out (also referred to as exclusion or cross-out) is a process by which antibodies are identified as being unlikely in a given sample because of the absence of an expected antigen-antibody reaction. In other words, the absence of a reaction is noted with a cell that is positive for the corresponding antigen. Non-reactive cells are selected for rule-out. To be classified as non-reactive, a cell must NOT have reacted in any phase of testing in a given panel or screen. In the case of cold antibodies: if reactions are only occurring at immediate spin and are negative in the AHG phase, then that panel cell can be used as a rule out cell for IgG reactive antibodies but not for antibodies that react at immediate spin (IgM).If there is no reaction with a panel cell then it is possible that antibodies to the antigens on that cell are not present in the sample being tested. Based on Fisher's statistical probability recommendation, the probability of having reliable results increases if you are able to have more rule-out and rule-in cells. By comparing the patterns of reactivity and non-reactivity, we can more safely assume that an observed pattern is not the result of chance alone. If a "3 (reactions) to rule in and 3 (reactions) to rule out" protocol is used, there is then a 95% probability that the reaction pattern is not due to chance alone. Homozygous cells are used so that weaker reacting antibodies which fail to react to the antigen present in the heterozygous state aren't accidentally ruled out. Examples of Homozygous and Heterozygous Antibodies Jka Jkb Patient IS Patient AHG Panel cell 10 + + 0 2+ Panel cell 11 0 + 0 4+ Panel cell 10 shows Jkb in the heterozygous state. The patient's reaction is weaker than the reaction with panel cell 11 which shows Jkb in the homozygous state.Reactions are weaker when antigens are present in the heterozygous state because there is less of the antigen present for the potential antibody to bind with.

Thalassemias are part of a group of hemoglobin synthesis disorders in which a defect exists in the rate of production of one or more of the globin chains. This defect results from either a heterozygous or homozygous deletion or inactivation of a globin chain gene.Thalassemias are named according to the affected gene or the globin chain that is showing reduced or absent synthesis.Globin chain loci are found on: chromosome 11 (beta, delta, epsilon, and gamma) chromosome 16 (alpha, and zeta)

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.

The prevalence of common HFE mutations among persons with hereditary hemochromatosis (HH) has been reported in numerous studies conducted in the US, France, Australia, and other countries. Homozygous C282Y mutation (C282Y/C282Y) is present in 82% to 90% of Caucasian patients diagnosed with iron overload due to HH.(7) This suggests a strong link between the genotype and the phenotypic presentation of clinical iron overload. Much lower percentages of persons diagnosed with HH do not have two C282Y mutations. A small percentage of persons diagnosed with HH are compound heterozygotes for C282Y and H63D (C282Y/H63D), are homozygous for H63D (H63D/H63D), heterozygous for C282Y (C282Y/wild type) or for H63D (H63D/wild type), or carry S65C or other HFE mutations.It may be that symptomatic heterozygotes are actually HFE-compound heterozygotes with additional unidentified mutations modifying the expression of the more severe known mutation. It is quite possible that more mutations of HFE and elucidation of other gene mutations modifying HFE will be discovered in the future enabling scientists to better explain the phenotypic heterogeneity of this disorder.In the US, the C282Y mutation is most prevalent in the non-Hispanic white population. It is much less common among Hispanics and African Americans.

The patient whose blood smear is shown in the photograph was a 32-year-old female from Virginia who came to the high country of Colorado to ski. The day after arrival, she experienced shortness of breath, fatigue, and upper abdominal pain. She was seen in a medical center in the mountains where a working diagnosis of altitude sickness was made. A CBC revealed RBCs 5.1 x 1012/L, hemoglobin 12.8g/dL, MCV 60fL, hematocrit 40.9%, and normal total WBC, differential, and platelet count. The RDW was normal. Further questioning revealed a previous diagnosis of heterozygous beta-chain thalassemia. No other abnormal hemoglobins were found on hemoglobin electrophoresis, but HbA-2 was elevated to 5%, supporting the diagnosis of beta thalassemia. The patient's poikylocytosis and anisocytosis may be a clue to an underlying erythrocyte abnormality. Persons with iron deficiency anemia may experience various degrees of hypoxia upon arriving at high altitudes. Those with sickle cell disease and thalassemia minor (as in this case) may experience bone pain or other symptoms of "crisis" and/or alteration in the appearance of their erythrocytes upon sudden high altitude exposure. The classic teaching is that in differentiating iron deficiency anemia from thalassemia, increased RDW would favor iron deficiency; normal RDW favors thalassemia.