The pattern of genetic inheritance in hemoglobin genes affects the clinical manifestations of beta-thalassemia.
|
Thalassemia Type |
Genetic Features |
|
thalassemia trait (variation) |
one beta-thalassemia gene mutation, mild |
|
thalassemia trait (variation) |
one beta-thalassemia gene mutation, severe |
|
thalassemia intermedia (variation) |
two beta-thalassemia gene mutations, both mild |
|
thalassemia intermedia (variation) |
two beta-thalassemia gene mutations, one mild and one severe |
|
thalassemia intermedia (variation) |
one beta-thalassemia gene mutation, mild AND excess alpha-globulin genes |
|
thalassemia intermedia (variation) |
one beta-thalassemia gene mutation, severe AND excess alpha-globulin genes |
|
thalassemia major |
one beta-thalassemia gene mutations, both severe |
|
hemoglobin E thalassemia (variation) |
one beta-thalassemia gene mutation, mild AND one beta-globulin gene with hemoglobin E mutation |
|
hemoglobin E thalassemia (variation) |
one beta-thalassemia gene mutation, severe AND one beta-globulin gene with hemoglobin E mutation |
Within each type the presence of other factors determines if the disease is more or less severe.
|
Thalassemia Type |
Ameliorating Factors |
Exacerbating Factors |
|
thalassemia trait |
concurrent alpha-thalassemia |
excess alpha-globulin genes (see below) |
|
thalassemia intermedia |
concurrent alpha-thalassemia; elevated hemoglobin F |
>= 5 excess alpha-globulin genes |
|
thalassemia major |
concurrent alpha-thalassemia; elevated hemoglobin F |
NA |
|
hemoglobin E thalassemia |
concurrent alpha-thalassemia; elevated hemoglobin F; mild beta-thalassemia gene mutation |
severe beta-thalassemia mutation |
where:
• I would expect the thalassemia intermedia with 1 severe mutation to be worse than the one with 2 mild mutations.
• The presence of thalassemia trait plus excess alpha globulin genes was classified as thalassemia intermedia in the genetic features.
Specialty: Hematology Oncology, Clinical Laboratory, Genetics
