Alpha thalassemia

on 4.3.09 with 0 comments

  • Will be expressed in feti, as chains are needed for HbF

  • In the newborn, the unpaired globulin chains form tetramers called Hb Bart's; in the adult, the excess globin chains form tetramers called HbH

  • There are 2 pairs of chain genes (i.e., 4 genes) on chromosome 16; the severity of the disease depends on how many genes are affected

    • Most common thing that goes wrong is a deletion; each gene contributes about 25% of the chains, and each can be deleted independently

    • A silent carrier state results from deletion of one gene

    • thalassemia trait comes from deletion of 2 genes

      • These patients may be slightly anemic, RBC microcytotic, but will have a normal electrophoresis, since all Hb types are equally affected

      • The genes can be form the same chromosome (Asian type) or can be one from each of the chromosomes (African type); those with the Asian type are at an increased risk of producing messed up kids

    • HbH disease

      • Deletion of 3 genes

      • Most common in Asian populations

      • Moderate in severity, it may be confirmed by showing HbH on electrophoresis or by staining of RBC inclusions by brilliant cresyl blue

    • Hydrops fetalis

      • All 4 genes gone

      • Without chains, HbF cannot be formed; the free chains form Hb Bart’s, which has a very high affinity for O2, not allowing it to be delivered to the fetus

      • Results in intrauterine death

Category: Medical Subject Notes , Pathology Notes



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