hematology and oncology
Thalassemias
Pathophysiology of Thalassemias
Thalassemia is a Overview of Hemoglobinopathies that is among the most common inherited disorders of hemoglobin production. The normal adult hemoglobin molecule (Hb A) consists of 2 pairs of chains designated alpha and beta. Normal adult blood also contains Alpha-thalassemia results from decreased production of alpha-polypeptide chains due to a deletion of one or more alpha genes. People normally have four alpha genes (two on each of a pair of chromosomes) because the alpha gene is duplicated. Disease classification is based on the number and location of deletions: Alpha + thalassemia:Loss of a single gene on one chromosome (alpha/--) Alpha 0 thalassemia:Loss of both genes on the same chromosome (--/--) Beta-thalassemia results from decreased production of beta-polypeptide chains due to either mutations or deletions in the beta globin gene, leading to impaired production of hemoglobin (Hb) A. Mutations or deletions may result in partial loss (beta + allele) or complete loss (beta 0 allele) of beta globin function. There are two beta globin genes, and patients may have heterozygous, homozygous, or compound heterozygous mutations. In addition, patients may be heterozygous or homozygous for abnormalities in 2 different globin genes (eg, beta and delta). Beta-delta-thalassemiais a less common form of beta-thalassemia in which production of both the delta chain as well as the beta chain is impaired. These mutations may be heterozygous or homozygous. 