A 12 month old female of Hawaiian, Chinese, Portuguese and Japanese ethnicity is noted to have a hemoglobin of 9.1 g/dl with an MCV of 58 on a routine CBC screen at her one year well child check up. She is otherwise healthy and has no complaints. PE is normal. On a review of this child's medical record, you note the presence of Hemoglobin Barts on her newborn screen.
Thalassemia is one of the most confusing of the hemoglobinopathies, mostly due to confusing nomenclature, lack of easy diagnostic tests, and its similarity to iron deficiency anemia. Whereas both thalassemia and iron deficiency anemia are characterized by microcytic hypochromic anemias, iron deficiency anemia is easily corrected with iron supplementation, but iron supplementation does not correct the anemia due to thalassemia. In any anemic state, there is increased gut absorption of iron. Even in non-transfused patients, iron overload is often noted in the more severe forms of thalassemia. Since thalassemia is not an iron deficiency problem, it is not be corrected by additional iron. In fact, in thalassemia over time, the body becomes iron overloaded, and iron is "stored" in the organs (liver, endocrine organs and heart), which can cause significant morbidity and mortality.
There are two basic types of thalassemia: alpha thalassemia and beta thalassemia. They have nothing to do with one another. Alpha thalassemia usually results from the deletion of any number of the 4 genes necessary to make alpha globin chains. Occasionally, an alpha globin gene is abnormal instead of being completely deleted. Beta thalassemia usually results from an abnormal gene in one or both of the genes necessary for beta globin chain production. Occasionally, the entire gene (on one allele) is actually deleted. The alpha and beta genes are located on different chromosomes and therefore, abnormalities of each are inherited separately.
Beta thalassemia usually occurs from abnormal beta genes, or less commonly, a deletion of a beta gene. In beta thalassemia, there is a large lack of normal beta chain production, thus causing a relative excess amount of alpha chains, which clump together. This abnormal hemoglobin is very unstable, and leads to erythrocyte death in the bone marrow.
Beta thalassemia minor occurs when only one gene is affected, causing a moderate, lifelong anemia. This typically requires no treatment other than recognition for the purposes of patient education, to avoid supplemental iron, and for genetic counseling.
Beta thalassemia major, historically called Cooley's Anemia, occurs when both genes necessary for beta globin production are affected. Since beta chains are not present in fetal hemoglobin, beta thalassemia does not manifest itself in newborns. Beta thalassemia presents at 6 months of age when adult hemoglobin has replaces fetal hemoglobin. Peripheral anemia, caused by the disease, sends signals to the bone marrow to increase production of erythrocytes (e.g., via erythropoietin), however, erythrocyte production is abnormal (ineffective). This process is called "ineffective erythropoiesis". With time, the marrow cavities (skull bones, facial bones, and ribs) expand, leading to the classical facial features and skull X-ray findings ("hair on end" in untreated patients due to excessive extramedullary hematopoiesis). Erythrocytes that do enter the circulation are noted to be abnormal by the reticuloendothelial system (spleen and liver), and are taken up by these organs with ensuing enormous hepatosplenomegaly. In untreated patients, death usually occurs by the end of the second decade of life from anemia and congestive heart failure.
Currently, part of the standard treatment for beta thalassemia major is lifelong transfusions given every 2-4 weeks. The intent of these transfusions is to keep their hemoglobin trough above 9 or 10 gm/dl. This will, in effect, shut off the patient's own erythropoiesis and stop the vicious cycle of anemia stimulating "ineffective erythropoiesis". With each milliliter of transfused packed red blood cells, the patient receives one milligram of elemental iron. Iron, in addition to being relatively difficult to absorb, is also not easily excreted. Thus, such transfused patients quickly become iron overloaded. Untreated, iron overload will be fatal. Regularly transfused patients need to be on lifelong chelation therapy to help their bodies excrete the excess iron. There are no effective oral iron chelation agents. Currently, most regularly transfused thalassemia patients receive their chelation as a subcutaneous infusion of deferoxamine over 10 hours each night (lifelong). With the combination of transfusion and chelation therapy, life expectancy can to be normal.
A form of alpha thalassemia occurs when any number of the four genes that control alpha globin production are missing, thereby causing an excess of non-alpha globin chains. The various forms of alpha thalassemia with their genetic correlate are listed below:
A. 4 normal alleles (normal)
B. 3 normal / 1 missing gene (silent carrier)
C. 2 normal / 2 missing genes (thal trait)
D. 1 normal / 3 missing genes ("Hemoglobin H disease")
E. 4 missing genes (results in hydrops fetalis)
Silent carriers are 1 missing alpha gene. They have no clinical abnormalities. Their hemoglobin, and hemoglobin electrophoresis are normal and their MCV is borderline normal.
Those with alpha thalassemia trait are clinically normal, but their hemoglobin is slightly low and their hemogram demonstrates microcytic indices. Their hemoglobin electrophoresis is normal unless it is done in the newborn period at which time Hemoglobin Barts is present (recall this finding in the case example at the beginning of the chapter).
Traditionally, people with alpha thalassemia trait are taught that they have a benign condition and no further education is provided. However, it should be emphasized that although the anemia is benign, supplemental iron must be AVOIDED to prevent harmful iron buildup. There is suspected sustained morbidity in persons with thalassemia trait, who are on repeated, or continued iron supplementation. Additionally, such iron supplementation is generally useless, even in menstruating females, as their stores are readily replenished by a greater degree of absorption of dietary iron from the gut. The extra iron is stored in the organs, leading to end organ dysfunction. Additionally, parents with this, so called, "benign" alpha thalassemia trait, can produce offspring with fatal hydrops fetalis if both parents pass on alleles with two defective alpha genes.
The name Hemoglobin H disease is a misnomer. In developed countries with otherwise good medical care, it is not a disease, but rather a condition. People with Hemoglobin H condition can live healthy, long lives. They are not transfusion dependent, as are those with beta thalassemia major. There are some rare variants, such as Hemoglobin H Constant Springs, (the Constant Springs is an abnormal gene, rather than a deletion, named after a U.S. city where it was first identified), that can be dependent on lifelong monthly transfusions. These people are missing 2 genes from one allele, and have the severely dysfunctional Constant Springs gene on the other allele. People with Hemoglobin H need to avoid all forms of supplemental iron, and pregnant women need very close prenatal care for their own health matters. Since the bone marrow of thalassemia patients requires excess folic acid (due to erythroid hyperplasia), most clinicians advise lifelong supplementation of 1 milligram daily of folic acid to avoid relative folate deficiency. During times of severe illness, or in pregnancy, the hemoglobin may drop significantly below baseline in Hemoglobin H disease, and a transfusion may be recommended. Again, iron is generally not deficient and, thus iron supplementation is not helpful, nor is it appropriate.
When four beta chains clump together, Hemoglobin H is formed. In infants, gamma chains predominate over beta chains, and Hemoglobin Barts (four gamma chains) is formed. Hemoglobin H and Hemoglobin Barts are both useless, with no effective oxygen carrying capacity. There has been a lot of confusion between this abnormal Hemoglobin H (4 beta chains clumped together) and the clinical condition in which 3 alpha genes are missing, called "Hemoglobin H disease or condition". The abnormal Hemoglobin H exists (in varying amounts) in all 4 clinical alpha thalassemia categories. Similarly in newborns, Hemoglobin Barts exists in varying amounts in all alpha thalassemia categories.
Hemoglobin H and Hemoglobin Barts do not cause the degree of ineffective erythropoiesis seen in beta thalassemia. Therefore, the classical "thal facies", "hair on end" skull X-rays, and enormous hepatosplenomegaly, all typical of beta thalassemia, are not seen to such degree in severe alpha thalassemia.
Hemoglobin E results from a single amino acid substitution on the beta globin chains. It is very common in the golden triangle of Laos, Cambodia, and Thailand. In the heterozygous form, it affects one out of three persons in this region. Heterozygous Hemoglobin E by itself is not harmful and causes no anemia. However, when combined with beta thalassemia minor, significant anemia develops over time. Such people usually become transfusion dependent later in the first decade of life, and if treatment is not sought or maintained, early death is most likely. The effects of Hemoglobin E on Hemoglobin H are not clear. Homozygous Hemoglobin E usually causes mild microcytic hypochromic anemia, which resembles alpha thalassemia trait.
1. In reference to the case presentation at the beginning of the chapter, what is the best approach to an otherwise healthy, asymptomatic 12 month old female with the hemoglobin of 9.1 g/dl (MCV 58) on routine CBC screen and the presence of Hemoglobin Barts on her newborn screen?
. . . . . a. explain to the parents that the baby may have thalassemia and obtain an electrophoresis.
. . . . . b. start the baby on Fe supplements and order an electrophoresis.
. . . . . c. start the baby on Fe supplements, recheck in a month, and if the hemoglobin is not improved then, assume the baby has thalassemia.
. . . . . d. counsel the family that the baby has a form of alpha thalassemia, and that no immediate other tests or Fe supplements are needed.
2. A 15 year old Filipino female is noted to have a hemoglobin of 10.6 g/dl with an MCV of 65 on routine testing. She reports regular menses lasting 4-5 days each cycle. She has no specific complaints. She is unaware of a family history of anemia. By history, her diet appears to be nutritionally adequate. PE is normal; specifically there is no hepatosplenomegaly, jaundice, or scleral icterus. What is the most appropriate management?
. . . . . a. start on oral contraceptives and recheck a CBC in two months
. . . . . b. start on empiric Fe while awaiting results of a hemoglobin electrophoresis and iron studies. Recheck CBC in 2 months if iron was deficient.
. . . . . c. check for Hemoglobin Barts; if not present start on Fe supplements and recheck CBC in 2 months
. . . . . d. order a hemoglobin electrophoresis; if Hemoglobin H is not found start on Fe while Fe studies are pending, and recheck CBC in 2 months if iron deficiency anemia was present
3. A newborn Laotian boy is noted to have Hemoglobin E on his newborn screen. He is otherwise well. A family history is not available due to a language barrier. What is the least pertinent issue to be considered here?
. . . . . a. presence of Hemoglobin Barts
. . . . . b. hemoglobin at 6 months of age
. . . . . c. hemoglobin level now
. . . . . d. the order of the hemoglobins printed on the newborn screen
4. Indicate whether iron supplementation is indicated or contraindicated in each of the following clinical situations.
. . . . . a. Menstruating female with a hemoglobin of 10.0 g/dl., with no known hemoglobinopathies.
. . . . . b. Beta thalassemia patient who just lost a modest amount of blood from a scalp laceration. Hemoglobin is 9.5 g/dl.
. . . . . c. Healthy alpha thalassemia trait male who wants to build up his hemoglobin to run a marathon.
. . . . . d. Menstruating female with alpha thalassemia trait who has had heavy and prolonged periods for the past year. Her hemoglobin is 8.0 and her iron levels and ferritin demonstrate severe iron deficiency.
5. Some ethnic groups with alpha thalassemia trait have a small risk of hydrops fetalis, but other groups have no risk. How is this possible? (The answer to this question was not stated in the chapter, but it can be answered with exceptionally brilliant thinking.)
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Answers to questions
1. Answer is d. Since the child had Hemoglobin Barts on the newborn screen, a form of alpha thalassemia is present. The hemoglobin of 9.1g/dl implies that it is likely Hemoglobin H thalassemia. There is no need to do a hemoglobin electrophoresis, since the type of thalassemia (alpha) is already known. Additionally, Hemoglobin H is so fast moving that it is typically missed on routine hemoglobin electrophoresis, thereby giving "normal" results. In general, therefore, hemoglobin electrophoresis is typically useless in evaluating for alpha thalassemia. This patient and her family should be provided with genetic counseling and education. She should be counseled to avoid supplemental iron, as a true iron deficiency is extremely rare in Hemoglobin H thalassemia. If iron deficiency is ever suspected, iron studies should be done to clearly document a true deficiency before iron supplementation is started.
2. Answer is b. The two most likely etiologies of the anemia in this young lady are iron deficiency or a form of thalassemia. She could most effectively be managed with a trial of iron (for one month). If a repeat CBC shows no change, then either alpha or beta thalassemia should be considered. A hemoglobin electrophoresis would be the next step if the iron trial fails. An increase in Hemoglobin A2 is very suggestive of beta thalassemia. In this case, the mild anemia would indicate a heterozygous beta thalassemia (beta thalassemia minor). Workup may stop there with proper genetic counseling and patient education. If the hemoglobin electrophoresis is normal, or near normal, then alpha thalassemia is the most likely cause.
3. Answer is C. The effects of Hemoglobin E are most significant when combined with beta thalassemia minor (see text), which is why the newborn's current hemoglobin (mostly fetal hemoglobin with no beta chains) is of the least concern. A CBC should be done at 9 or 12 months of age to screen for coexisting beta thalassemia.
4a. Fe is indicated as a therapeutic trial. But if no improvement in the hemoglobin results, then a thalassemia is possible.
4b. Fe is contraindicated since it will not improve the hemoglobin and it will add to the potential for iron toxicity.
4c. Fe is contraindicated, since it will not improve his hemoglobin and it will add to the potential for iron toxicity.
4d. Despite the presence of thalassemia, iron deficiency is documented by laboratory studies, so iron supplementation is indicated until iron deficiency resolves. Once iron deficiency is no longer present, iron supplements become contraindicated.
5. The four alpha genes are not inherited independently. They are inherited in pairs on each chromosome. Thus, a patient with alpha thal trait who has two defective alpha genes and two normal alpha genes could have this in one of two ways: 1) AX/AX, or 2) AA/XX, where "A" is a normal alpha gene and "X" is a defective alpha gene. Some ethnic groups have the genes arranged in the first form only, in which case, two parents with alpha thal trait would always pass AX to their child resulting in a child with AX/AX (alpha thal trait). Fetal hydrops (XX/XX) could never result from such a genetic arrangement. However, if both parents with alpha thal trait were AA/XX, then their children could either be: AA/AA, AA/XX, or XX/XX (fetal hydrops).