Introduction
Hemoglobinopathy is a hemoglobin disorder that is characterized by altering the structure and function of the hemoglobin molecule. It is an inherited condition affecting the red blood cells and the molecular structure of hemoglobin molecules. The condition occurs due to genetically determined changes in the hemoglobin molecular structure. The disease manifests itself in the form of mild anemia in beta-thalassemia, severe episodic pain, retarded growth development, frequent occurrence of infections, and chronic anemia in sickle cell anemia (Hemoglobin SS) and beta-thalassemia patients. Hemoglobinopathy is genetically inherited in an autosomal recessive pattern.
What Are the Types of Hemoglobin?
Hemoglobin is a tetramer molecule that comprises two alpha-globin and two non-alpha-globin chains which work in association with heme to carry the oxygenated blood to the tissues in the body. There are various types of hemoglobin including adult hemoglobin HbA and HbA2, HbE, HbF (fetal hemoglobin), HbS (sickle cell), HbC, HbH, and HbM (methemoglobin) are present. Only HbA and HbA2 types of adult hemoglobin are found in considerable levels in healthy individuals. Rarely, in a few cases, small levels of HbF are also present.
What Are the Types of Hemoglobinopathies?
The various types of hemoglobinopathies include:
1. Sickle cell disease (HbS).
2. Sickle cell trait (HbAS).
3. Sickle cell-hemoglobin C (HbSC).
4. Sickle cell-thalassemia (HbS and HbA).
5. Hemoglobin C disease (Hb CC).
6. Hemoglobin C trait (HVAC).
7. Thalassemia.
a) Alpha thalassemia (deficient alpha-globin chain synthesis).
b) Beta thalassemia (deficient beta-globin chain synthesis)
- Thalassemia major (homozygous) - Cooley anemia.
- Thalassemia minor (heterozygous).
What Are the Causes of Hemoglobinopathies?
It is an autosomal recessive hereditary disorder.
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Occlusion of blood vessels leading to infarcts.
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Necrosis (cell death).
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Pathologic bone fractures.
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Osteomyelitis (more common in sickle cell disease patients).
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Sickle cell disease is a type of hemoglobinopathy that is caused by abnormal hemoglobin production which causes damage and deformation of the red blood cells. These abnormal red blood cells break down thereby causing sickle cell anemia, and occlude the blood vessels, thereby leading to repetitive episodes of severe pain and multi-organ failure.
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Alpha thalassemia is caused due to an alteration or mutation in a gene or deletion of the gene that is associated with the alpha globin protein.
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Beta thalassemia occurs due to a mutation in the beta-globin gene thereby affecting the production of the beta-globin protein.
What Are the Clinical Features of Hemoglobinopathy?
The signs and symptoms occur due to decreased oxygen-carrying capacity of the blood to the body tissues. The condition includes the following:
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Muscle pain due to lack of oxygen supply (claudication).
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Increased heart rate (tachycardia).
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Reduced breathing (dyspnea).
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Vertigo (spinning head).
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Angina (chest pain).
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Sleeping longer than usual.
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Fatigue.
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Swelling and pain in the upper and lower extremities.
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Cold feet.
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Pale skin.
What Is the Epidemiology of Hemoglobinopathies?
Sickle cell disease is a type of hemoglobinopathy that is typically common in people whose ancestors derive their origin from sub-Saharan Africa, Central and South America, the Caribbean region, Saudi Arabia, India, and the Mediterranean areas like Greece, Italy, and Turkey. Alpha thalassemias commonly occur in individuals from the Middle East, Southeast Asian countries, China and Africa. Beta thalassemias are most commonly present in individuals living around the Mediterranean region.
What Are the Radiographic Features of Hemoglobinopathies?
The radiographic features of hemoglobinopathies in general may be described as:
1. Extramedullary Hematopoiesis:
- Metaphyseal flaring.
- Hair end-on appearance.
- Rib expansion.
- Widening of diploe.
- Thinning of the outer table.
- Facial bone changes.
- Sinus obliteration.
- Hypertelorism.
- Displacement of teeth.
2. Infarctions:
- Ischemia in the femoral head.
- Retarded growth.
- Hemorrhage in the joint space.
- Hand-foot syndrome.
How Is Diagnosis of Hemoglobinopathy Established?
For the diagnosis of hemoglobinopathies, the hemoglobin isoelectric focusing and high-performance liquid chromatography tests are performed to demonstrate various hemoglobin disorders of varying severity. For screening purposes, dried blood spots and liquid whole blood samples are usually collected. Ethylene diamine tetra acetic acid (EDTA) is the anticoagulant used for the collection of whole blood. For dried blood spot collection, the palmar surface of the last finger is most commonly used. Blood smears are not recommended for hemoglobinopathy screening since it requires the presence of circulating sickled cells.
Methods:
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Isoelectric Focusing- This technique separates the hemoglobin proteins in a gel medium. The globin proteins migrate to a region in the gel medium where the pH of the gel matches the pH of the hemoglobin. This technique is used to differentiate the different types of hemoglobin.
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High-Performance Liquid Chromatography- This technique separates the hemoglobins by a cartridge using a buffer gradient having increasing ionic strength. The fractions of hemoglobin separate depending on their ionic strength within the cartridge. This technique is good for differentiating HbF and HbA2 along with screening for thalassemia patients. This technique is also used to identify hemoglobinopathies in newborns.
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Molecular Methods- Deoxyribonucleic acid sequencing, and polymerase chain reaction procedures can be used to identify the hemoglobinopathies.
What Is the Treatment of Hemoglobinopathy?
Antibiotic prophylaxis is recommended by doctors to begin at two months of age and continue till early childhood. In the case of fever, prompt management of the illness should be done to mitigate the occurrence of a sickling crisis. Pain management therapy including the use of extra fluids, pain analgesics, and other measures should be undertaken. A blood transfusion may be required in certain cases. Certain medications are provided that will increase fetal hemoglobin production in children.
However, a blood or bone marrow transplant is the only known treatment for sickle cell disorder. Bone marrow transplantation has serious threats and is only suggested in patients suffering from severe pain or other symptoms. The diseased blood-forming cells are replaced with healthy ones in transplant cases. Usually, an allogeneic transplant is used. Healthy blood-forming cells are derived from a family member, a donor, or an umbilical cord blood unit in this type of transplant. Chemotherapy is provided in patients before the process of transplantation. Then, the healthy replacement cells are infused within the bloodstream of the patient. The cells then make their way into the bone marrow. They then start generating healthy white blood cells, red blood cells, and blood platelets. The entire process usually takes weeks followed by months of follow-up.
Conclusion
Hemoglobinopathy is a genetic disorder affecting the oxygen-carrying capacity of hemoglobin. It is a serious disease. It is important to do newborn screening for this set of disorders. The affected patients should be given adequate care. More research is required in the field of diagnostic and therapeutic measures to improve the overall prognosis of the disease.
