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Abnormal Haemoglobins: Thalassaemia - Coggle Diagram
Abnormal Haemoglobins: Thalassaemia
Thalassaemias
Causes
Mutations in globin chain gene
Decreased globin chain production
Disordered globin synthesis
Decreased Hb synthesis due to:
Structural gene deletions
(a-thalassaemia)
Mutations
preventing gene expression
(B-thalassaemia)
B-Thalassaemia
Imbalance of a and B globin chains
Decreased rate of synthesis of B globin chains
Unpaired a globin chains (precipitate to form
Heinz bodies
)
Causes oxidative stress & damage to cell membranes
Apoptosis of RBC precursors in BM
Phagocytosed by macrophages
Ineffective erythropoiesis
BM attempts to produce RBCs
Lab Testing
FBC - Hb & RCC indices decreased
Peripheral blood film
Hb electrophoresis
Molecular testing (DNA analysis) - detection of thalassaemia mutations
Clinical Features
Increases in HbA2 & HbF
Haemolytic anaemia
a-Thalassaemia
Group of disorders
Excess y chains: Tetramer of y chains (Hb Barts)
Excess B chains: Tetramer of B chains (HbH)
Lab Testing
FBC - Hb & RBC indices decreased
Peripheral Blood - Microcytic Hypochromic anaemia (MCV < 75 fL)
Poikilocytosis
Anisocytosis
Further lab testing
HbH inclusions (supravital
stain, e.g., methylene blue)
Molecular testing (DNA analysis)
Haemoglobinapthies
Disordered Hb structure
Sickle Cell Disease (HbS) Disease
Sickle cell trait (Heterozygous - AS)
Sickle cell anaemia (SCA) - Homozygous SS
Blood film
Normocytic/normochronic anaemia
Microcytosis
Polychromasia
Anisocytosis
Poikilocytosis -
sickle cells
, target cells, basophilic stippling, NRBCs
Identification
Hb Electrophoresis
HPLC
HbC
Haemolytic anaemia (milder than HbSS)
Microcytic/hypochromic; codocytes, polychromasia
HbC polymerises under low O2 tension
HbC crystals
HbE
Codocytes (+++)
Mild microcytic/hypochromic anaemia