Thalassemia
From IDWiki
Background
- A group of usually inherited hemoglobinopathies characterized by either reduced (+) or absent (0) production of globin chains (either α or β chains)
- Causes a microcytic anemia characteriezd by chronic hemolysis (with anemia, gallstones, aplastic crisis), decreased erythropoiesis (due to apooptosis of erythroid precursors), increased iron absorption (cirrhosis, cardiomyopathy, endocrinopathies)
- Severity varies widely
| α-Thalassemia | β-Thalassemia | ||||||
|---|---|---|---|---|---|---|---|
| Silent/Minima/Carrier | Trait/Minor | Hb H | HB Barts | Trait | Intermedia | Major | |
| Epidemiology | Southern China, Malaysia, and Thailand, as well as trait in Africa | Africa and the Mediterranean | |||||
| Pathophysiology | -α/αα | -α/-α or --/αα | --/-α
formation of Hb H (β4 tetramer) |
--/--
formation of Hb Barts (γ4 tetramer) |
β+/β or β0/β | β+/β+ or β0/β+ | β0/β+ or β0/β0 |
| CBC and film | Normal CBC | Mild microcytic anemia | Moderate microcytic anemia | Fatal in utero (hydrops fetalis) | Slight microcytic anemia, elevated HbA2 | Late onset (>2 years), Hb 70-100 g/L, not transfusion dependent | Diagnosed in infancy, Hb <70, transfusion dependent |
| Hemoglobinalysis | Can show Hb H (up to 30%) in Hb H disease, or 3-8% Hb Barts in minor; silent carrier has normal | HbF elevated (up to 95% in major, 50% in intermedia, 5% minor); elevation of HbA2 >3.5% | |||||
Investigations
- CBC
- Compared to iron deficiency anemia, RDW tends to be narrower, MCV tends to be smaller, and RBC tends to be high or normal (as opposed to decreased)
- Thalassemia index = MCV/RBC; if less than 13, suggests thalassemia over iron deficiency
- Normal WBC and platelet counts
- Blood film: Microcytic target cells
- Iron studies: Normal or elevated ferritin, with elevated iron saturation (and decreased TIBC)
- Hemoglobin electrophoresis
- Hb H may be seen in α-thalassemia, but it can also be normal
- HbA2 greater than 3.5% suggests β-thalassemia
- Molecular studies
