Альфа-талассемия: Диагностика, проявления и лечение.

Thalassemia involving the genes HBA1and HBA2 hemoglobin genes
!Common
!Uncommon
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Anemia: People with alpha thalassemia can experience both a decrease in the production of red blood cells (RBC) and an increase in the destruction of RBCs which can result in other symptoms such as fatigue and dizziness. Enlarged spleen
Gallstones
Delayed growth
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Jaundice
Pronounced forehead: This occurs due to the expansion of the bone marrow in the frontal bone in the skull. Alpha thalassemia can also be acquired under rare circumstances.

The mechanism sees that α thalassemias results in decreased alpha globin production, therefore fewer alpha globin chains are produced, resulting in an excess of β chains in adults and excess γ chains in newborns. The excess β chains form unstable tetramers called hemoglobin H or HbH of four beta chains. The excess γ chains form tetramers which are poor carriers of O2 since their affinity for O2 is too high, so it is not dissociated in the periphery. Homozygote α0 thalassaemias, where numerous γ4 but no α globins occur at all (referred to as Hb Barts), often result in death soon after birth.

Diagnosis of alpha thalassemia is primarily by laboratory evaluation and molecular diagnosis. Alpha thalassemia can be mistaken for iron deficiency anaemia on a full blood count or blood film, as both conditions have a microcytic anaemia. Serum iron and serum ferritin can be used to exclude iron deficiency anaemia.

The ability to measure hemoglobin Barts makes it useful in newborn screening tests. If hemoglobin Barts is detected on a newborn screen, the patient is usually referred for further evaluation since detection of hemoglobin Barts can indicate either one alpha globin gene deletion, making the baby a silent alpha thalassemia carrier, two alpha globin gene deletions (alpha thalassemia), or hemoglobin H disease (three alpha globin gene deletions). Deletion of four alpha globin genes was previously felt to be incompatible with life, but there are currently 69 patients who have survived past infancy. All such children too show high level of hemoglobin Barts on newborn screen along with other variants. Post newborn ages, initial laboratory diagnosis should include a complete blood count and red blood cell indices. Hemoglobin analysis is important for the diagnosis of alpha thalassemia as it determines the types and percentages of types of hemoglobin present. Several different methods of hemoglobin analysis exist, including hemoglobin electrophoresis, capillary electrophoresis and high performance liquid chromatography. Splenectomy is a possible treatment option to increase total hemoglobin levels in cases of worsening anemia due to an overactive or enlarged spleen, or when transfusion therapy is not possible. However, splenectomy is avoided when other options are available due to an increased risk of serious infections and thrombosis. Additionally, stem cell transplantation should be considered as a treatment (and cure), which is best done in early age. Other options, such as gene therapy, are still being developed. A study by Kreger et al combining a retrospective review of three cases of alpha thalassemia major and a literature review of 17 cases found that in utero transfusion can lead to favorable outcomes. Successful hematopoietic cell transplantation was eventually carried out in four patients.

Worldwide distribution of inherited alpha thalassemia corresponds to areas of malaria exposure, suggesting a protective role. Thus, alpha thalassemia is common in sub Saharan Africa, the Mediterranean Basin, and generally tropical (and subtropical) regions. The epidemiology of alpha thalassemia in the US reflects this global distribution pattern. More specifically, HbH disease is seen in Southeast Asia and the Middle East, while Hb Bart hydrops fetalis is acknowledged in Southeast Asia only. The data indicate that 15% of the Greek and Turkish Cypriots are carriers of beta thalassaemia genes, while 10% of the population carry alpha thalassaemia genes.