Alpha Thalassemia (3)

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 (--/a^csa) 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>

<page 1> <page 2> <page 3> <page 4>