Hi everyone!
I'm not new to understanding thalassemia but I'm new to understanding how the different thalassemias are classified/categorized and what terms and definitions people use to describe them.
I always thought thalassemia in itself was the umbrella term for both alpha and beta thal and yet I most often hear the term thalassemia used in reference to beta thal only, which I guess is because thal major is a beta thal.
But because of this interesting discrepancy I've been noticing, I'm wondering where do the alpha thals fit in? I don't have Thalassemia Intermedia because my condition is an intermediate form of an alpha thal and not a beta thal and yet, if we use thalassemia as an umbrella term for both beta and alpha thal, then I would fit in because my thalassemia is an intermediate form.
I'm confused.
I've been comparing literature on Thalassemia Intermedia and Hemoglobin H disease and where the literature notes some differences, I'd like to know what everyone else here thinks about the differences between Thal Intermedia and HgH Disease and about how people use which terms to classify the types of thalassemias.
Here's some literature on HgH Disease:
Hemoglobin H disease is characterized by one functional gene that codes for the production of alpha globins (--/-a). Hgb H disease should be considered in the case of a neonate in whom all of the red blood cells are very hypochromic. These neonates have a high percentage of hemoglobin Bart's on the their newborn screening results. In older children, this hemoglobinopathy is characterized by moderate anemia with a hemoglobin in the 8 to 10 gm/dL range, hypochromia, microcytosis, red cell fragmentation, and a fast migrating hemoglobin (Hgb H) on electrophoresis.
Hemoglobin H does not function as a normal hemoglobin and has a high oxygen affinity (holds onto oxygen longer making it unavaible for use by the body), so the measured hemoglobin in these children is misleading. Individuals who have Hgb H generally have a persistent stable state of anemia, which may be accentuated by increased hemolysis during viral infections and by exposure to oxidant medications, chemicals and foods such as sulfa drugs, benzene, and fava beans (similar to individuals who have G6PD deficiency). As the red cells mature they loose their ability to withstand oxidant stress and Hgb H precipitates, leading to hemolysis. Therapy for individuals who have Hgb H disease includes folate, avoidance of oxidant drugs and foods, genetic counseling education and frequent medical care. Uncommon occurrences in a child with Hgb H would be severe anemia, cholelithiasis, skin ulceration, and splenomegaly requiring splenectomy. Unlike individuals who have beta thalassemia, hemosiderosis is rare in Hgb H disease.
Children with Hemoglobin H-Constant Spring (--/acsa) have a more severe course than children who have Hgb H. They have a more severe anemia, with a steady state hemoglobin ranging between 7 and 8 gm/dl. They more frequently have splenomegaly and severe anemia with febrile illnesses and viral infections, often requiring transfusion. If anemia is chronically severe and the child has splenomegaly, a splenectomy may be performed. If splenectomy is anticipated, the complication of severe post-splenectomy thrombocytosis with hypercoagulability can occur, leading to thrombosis of the splenic vein or hepatic veins. This complication has also been reported as recurrent pulmonary emboli and clotting diathesis. At CHO, children who are scheduled to have surgery are treated pre-surgically with low molecular weight heparin, followed by low dose aspirin, continued indefinitely. <next>
And here's literature on Thalassemia Intermedia.
Children who are diagnosed with Thalassemia Intermedia have a homozygous or heterozygous beta globin mutation that causes a decrease in beta chain production, but not to the degree that chronic transfusion therapy is required. The phenotype can also occur in children who have a mutation that increases production of c-globin, in children who have co-inherited alpha thalassemia and beta thalassemia, and in other rarer mutations. Children who have thalassemia intermedia are able to maintain a hemoglobin of 7 gm/dl or slightly higher with a greatly expanded erythron and may manifest bony deformities, pathologic fractures and growth retardation. Children who have thalassemia intermedia can also have delayed pubescence, exercise intolerance, leg ulcers, inflammatory arthritis and extramedullary hematopoiesis causing spinal cord compression, a medical emergency requiring radiation therapy and transfusion. They can also have iron overload due to increased absorption of iron from the gastrointestinal tract and intermittent transfusion. They are at risk for the cardiac and endocrine complications of hemosiderosis, but usually at an older age than chronically transfused children. Chelation therapy is indicated for increasing ferritin and elevated liver iron.
Children who can not maintain a hemoglobin between 6 and 7 gm/dl should have an alternative diagnosis considered. If thalassemia is the cause of the anemia, transfusion and/or splenectomy should be considered. Frequently, adolescents and adults are unable to tolerate the degree of anemia that is seen in thalassemia intermedia. Hypersplenism, splenic pain, congestive heart failure secondary to anemia, severe exercise intolerance, thrombocytopenia and leukopenia should be considered indications for beginning transfusion therapy or for splenectomy in the child who has severe hemolytic anemia. <next>
There are obvious differences and yet a lot of similarities.
My question is, what are the causes of the differences?
Is it the differences in hemoglobin levels?
Is it differences in other cell functions?
My own HgH gives me a persistent state of anemia with a 7.X hemoglobin count. Experiences I've had are quite similar to those who have Intermedia, which leads me to believe that perhaps a lot of the issues come from Hg levels, but of course, I really have no idea.
Anyone have any insight?