Master's in Genetic Counseling (MGC)
Hemoglobinopathies
Hemoglobinopathies are a group of autosomal recessive conditions characterized by abnormalities in the structure of hemoglobin, most often affecting the β globin chain of adult hemoglobin. Sickle cell disease is the most common hemoglobinopathy and results from abnormal structure of the hemoglobin molecule, while thalassemias result from decreased synthesis of normal globin chains.
Clinical Features
Sickle cell anemia is the most common hemoglobinopathy and results from a homozygous mutation of β hemoglobin (SS hemoglobin). Infants appear normal at birth, and clinical symptoms may not develop for months or years. Symptoms and associated problems include fever, sepsis, anemia, jaundice, splenic sequestration, dactylitis, aseptic necrosis of bones, acute chest syndrome, leg ulcers, stroke, retinopathy, and renal concentrating defects.
In other hemoglobin disorders, the clinical presentation varies with respect to the type of hemoglobin variant present. Manifestations may range from mild hemolytic anemia with microcytosis to severe forms of hemolysis that are transfusion dependent.
Most heterozygotes do not experience clinical problems. Identification of these individuals, along with appropriate genetic counseling, allows for the identification of couples at risk and for testing of other family members. (OMIM)
Laboratory Tests
Screening for hemoglobinopathies is performed by separating the different types of hemoglobin and estimating the relative concentration of each type. A normal result is one in which fetal and adult hemoglobin are present (FA). All other results require additional testing for confirmation. Solubility testing (sickle prep or sickle dex) is not sufficient as a confirmatory test. Referral to a pediatric hematology consultant for additional testing and management is recommended.
Treatment
With recognition and appropriate treatment of the hemoglobinopathies, complications can be minimized. Management approaches consist of educating affected families about the disorders, prompt emergency care for fever and infections, appropriate immunizations (including Pneumococcal polysaccharide vaccine and trivalent influenza virus vaccine), penicillin prophylaxis, and management of the anemia. For specific treatment guidelines, consultation with a pediatric hematologist is strongly recommended.
Screening Practice Considerations
Detection of hemoglobinopathies does not depend on the age of the infant or diet. However, specimens must be collected prior to any blood transfusions, as this may lead to a false negative result. If a transfusion has taken place before specimen collection, a repeat specimen should be obtained 90 to 120 days after the last transfusion.
Current screening tests do not detect many infants with thalassemias. Clinical suspicion should dictate further testing and consultation regardless of previous normal screening test results.
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