Types of Thalassemia

Alpha Thalassemia

Alpha thalassemia refers to a group of disorders characterized by inactivation of alpha globin genes. This results in a relative increase in nonfunctional beta globin or gamma globin tetramers and subsequent cell damage. Normally, there are four alpha genes. Absence or non-function of three alpha genes results in hemoglobin H disease, and the loss of all four alpha genes usually results in intrauterine death. Frequently, the diagnosis of alpha thalassemia trait in a parent is discovered after the birth of an affected child.The alpha thalassemias can be generally categorized as:

  • Silent Carrier
  • Alpha Thalassemia Trait
  • Hemoglobin H disease
  • Hemoglobin H-Constant Spring
  • Alpha Thalassemia major

Beta Thalassemia

 Individuals who have beta thalassemia major are usually homozygous for one of the common mutations, or heterozygous for one of the common mutations and one of the geographically-unique mutations. Both lead to absence of beta globin chain production. The beta thalassemia syndromes are much more diverse than the alpha thalassemia syndromes due to the diversity of the mutations that produce the defects in the beta globin gene.

Hemoglobin H disease

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 disease and its variants:

  • Hemoglobin H deletion
  • Hemoglobin H–Constant Spring
  • Homozygous alpha-thalassemia