7/20/2023 0 Comments Precipitate definition for kids![]() Point mutations also may occur in the alpha thalassemia genes which reduce or stop alpha globin production as well. The cis orientation is more common in Asians while the trans orientation is more common among people of African ancestry. In the trans orientation one alpha globin gene is deleted on both chromosome 16s. The deletions can occur in both the cis and trans orientations. Some alpha globin gene deletions remove both alpha globin genes (alpha thalassemia trait). Some alpha globin deletions remove one gene (silent carrier state). There are two genes for alpha globin production on each chromosome. The genes for alpha globin are on chromosome 16. People of southern Chinese, Mediterranean, Asian Indian, and Middle Eastern ancestry are also commonly found to be carriers. The greatest incidences of heterozygotes (carriers) are found in African Blacks (one in 30 births) and Southeast Asians (one in 20 births). Vietnamese, Thai, Filipine and, to a lesser degree, Middle Eastern ancestry. The prevalence of HbH disease is highest in Laotian and Cambodian newborns, but is also seen in infants of Chinese, states with ethnic populations similar to Illinois. Hemoglobin H disease affects as many as one in 15,000 births in some U.S. Health care monitoring and maintenance with appropriate immunizations are important as well. Infections should to be monitored closely so any severe drop in hemoglobin can be recognized and treated. Complications related to chronic hemolysis also need to be assessed. Hemoglobin levels and the patient’s growth and development should be regularly monitored. Hemoglobin H disease has a wide spectrum of clinical severity in patients, therefore, early diagnosis is important so patients can be followed. Genetic counseling services should be offered to parents. All siblings of an infant diagnosed with a Hemoglobin H disease should be tested. Hemoglobin electrophoresis including both cellulose acetate and citrate agars (one is not sufficient), isoelectric focusing and high performance liquid chromatography are considered proven, reliable and accurate methods for defining an infant’s hemoglobin phenotype. There are several recommended testing methods for diagnosis of hemoglobinopathies such as Hemoglobin H disease. Neonates who are transfused after birth should have their newborn screening repeated post-transfusion in the time frame recommended by IDPH. Transfusions may alter the newborn screening test results for Hemoglobin H disease. Referral to a pediatric hematologist for diagnosis within the first month of life is recommended and should not be delayed until the infant is older. All abnormal newborn screening test results indicating Hemoglobin H disease require appropriate confirmatory blood tests which may included testing of the parents. HPLC has been shown to be effective for detecting hemoglobinopathies characterized by synthesis of an abnormal hemoglobin molecule immediately after birth. Samples with 25 percent or greater of Bart’s hemoglobin (gamma tetramers) are considered suggestive of Hemoglobin H disease. In Illinois, newborn screening for Hemoglobin H disease is performed by high performance liquid chromatography (HPLC) testing to determine the amount of Bart’s hemoglobin present. Newborn Screening and Definitive Diagnosis Severe iron overload can occur over time with HbH disease, even in minimally or non-transfused patients. ![]() Co-inheritance of HbH with other globin defects can result in a more severe chronic anemia for which monthly transfusions are needed. Episodes of hemolysis may be brought on by drugs or infections. Others may experience gallstones and leg ulcers. ![]() Some may develop the facial and other skeletal deformities more commonly associated with beta-thalassemia. Signs of hemoglobin H disease include a moderate anemia in the range of 7-10 g/dL with marked microcytosis, jaundice and hepatosplenomegaly. Some children with HbH disease, however, will have poor growth. Infants with hemoglobin H disease are normal at birth and generally remain so. Co-inheritance of HbH with other globin gene defects can affect the severity of the condition. Hemoglobin H is a thalassemia-like syndrome characterized by hemolysis as well as ineffective red cell production. This leads to an excess of beta globin chains, which are unstable, precipitate within the cell and lead to destruction of the red blood cells. Hemoglobin H disease is an inherited hemoglobin disorder in which three of the four alpha globin genes normally present are deleted or have a mutation which impairs alpha globin chain production. (Alpha Thalassemia) Information for Physicians and ![]() Newborn Screening Program - Homocystinuria ![]()
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