Extramedullary Hematopoeisis
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Morning Report June 17th 2005
Wassim Mchayleh, MD
Thalassemias
Hemoglobin structure• Hb - tetramer of 2 -like and 2 -like
proteins
• Normal Hb– Adult (major): HbA -
(minor): HbA2 -
– Fetal: HbF -
– Embryonic: Hb Gower I -
Demographics: Thalassemia
• Found most frequently in the Mediterranean, Africa, Western and Southeast Asia, India and Burma
• Distribution parallels that of Plasmodium falciparum
α-Thalassemia
• α-Thalassemias are common in Africans and Southeast Asians; up to 30% in black Americans
• Phenotype depends on the number of intact α-globin genes.
SymbolismAlpha Thalassemia
• Greek letter used to designate globin chain:
SymbolismAlpha Thalassemia
/ : Indicates division between genes inherited from both parents:
/
• Each chromosome 16 carries 2 genes. Therefore the total complement of genes in an individual is 4
SymbolismAlpha Thalassemia
- : Indicates a gene deletion:
-/
Classification & TerminologyAlpha Thalassemia
• Normal / • Silent carrier -/ • Minor -/-
--/• Hb H disease --/- (moderate to
severe hypochromic microcytic anemia)• Barts hydrops fetalis --/--
Special Cases: Thalassemia
• Hb H• 4 tetramer• Associated with --/- thalassemia• Moderate to severe hypochromic microcytic
anemia
Special Cases: Thalassemia
• Hb Barts & hydrops fetalis • Barts is a 4 tetramer• Associated with --/--• Lethal
B-Thalassemia
• observed in Mediterranean, sub-Saharan African and Indian descents
SymbolismOther Thalassemia
• Greek letter used to designate globin chain:
SymbolismOther Thalassemia
+: Indicates diminished, but some production of globin chain by gene:
+
SymbolismOther Thalassemia
0 :Indicates no production of globin chain by gene:
0
Classification & Terminology Beta Thalassemia
• Normal /
• Minor /0
/+
• Intermedia 0/+
• Major 0/0
+/+
-Thal Major• Well at birth
• Symptoms start after 6 months with the loss of HbF( ).
• Severe hemolytic anemia with Jaundice, Hepato-Splenomegaly.
• Symptoms from ineffective erythropoiesis bony abnormalities and abnormal skeletal development .
-Thal Minor
• Microcytic hypochromic anemia
• Ht >30 percent ,MCV <75 and normal RDW with high RBC count will differentiate it from Iron deficiency anemia
• Splenomegaly in 10-20%
• Target cells on peripheral smear
-Thal Intermedia
• Symptomatic patients who do not require transfusions
• Increased dietary iron absorption with possible iron overload
• Smptoms of chronic hypoxia( Pulm HTN,CHF)
• Extra-medullary Hematopoiesis
Primary Laboratory InvestigationThalassemia
• Severe cases present with
• Microcytosis
• Hypochromia
• Poikilocytosis
• Tear drops and Target cells
• RBC counts higher than expected for the level of anemia
Laboratory evaluation
• Hemoglobin electrophoresis for diagnosis
• Hb H in severe -thalassemia
• Elevated Hb A2 levels in -thalassemia
• Formal genetic analysis can be necessary to distinguish between them.
Course and TreatmentThalassemia
• Time of presentation
• Related to degree of severity
• Usually in first few years of life
• Untreated severe thalassemia
• --/--: Prenatal or perinatal death
• --/- & --/cs: Normal life span with chronic hemolytic anemia
Course and TreatmentThalassemia
• Untreated thalassemia
• Major: Death in first or second decade of life , chronic transfusion required with iron chelating therapy (Desferrioxamine)
• BMT can be a curable treatment
• Intermedia: Usually normal life span
• Minor/Minima: Normal life span
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