Transcript Hemoglobinopathies

Hemoglobinopathies
Mark D. Browning, M.D.
March 8, 2017
Hemoglobin
Normal Hemoglobin
• 2 alpha chains
– 141 amino acids
• 2 beta chains
– 146 amino acids
• These 4 polypeptide chains form a helical
structure
– Hydrophobic pockets…holding four heme groups
• Central cavity…between…2 beta globin chains
houses 2-3 DPG
Hemoglobin Electrophoresis
*Hemoglobinopathies
• Single amino acid substitution
– Can interfere with the helical structure
– Can make the globin unstable
• Most Common
– Sickle cell disease…amino acid valine #6
substitution results in dramatic change in
solubility
• Deoxy state Hgb S depolymerizes..forms twisted
ropelike fiber & deforms RBC shape
25yo African American Female
• Hgb S = 83%, Hgb F = 12%, Hgb A2=5%
• Mother ?, Father AS, Sister SS, 2 sibs
without disease
• Hgb maintained at 10 unless crisis
• Crisis= 6 to 7 Hgb
– Retic 6 to 15%
– Increase Bili & LDH
Hemoglobin SS
25 yo Female with SS
Urine Specific Gravity
• 1.005, 1.005 & 1.015 on 3 different
occasions
– Normal specific gravity 1.001-1.035
*Hemoglobinopathies
• > 400 Hemoglobin variants defined
– > ½ are clinically silent
– Heterozygotes present with mild effect
– Homozygotes present with moderate to severe
effect
• Hemolytic anemia
• High oxygen affinity…erythrocytosis
• Low oxygen affinity…cyanosis
Hemoglobinopathies
• Thalassemias
– Quantitative defect in globin synthesis
involving gene mutation or defect
• Sickle Cell Disease & Hgbs C, D, & E
– Qualitative (structural) defect in amino acid
substitution in the globin chain
*Hemoglobinopathies
Most Common
• Hgb S, C, D & E
– Present in their homozygote form, results in severe
disease…SS, CC, DD, EE
– Present in their heterozygous form, results in mild
disease…AS, AC, AD, AE
• Hemoglobin electrophoresis
– Confirms diagnosis (Figure 7-2)
– Confederate States of America (CFSA)…all but A2
hemoglobin on cellulose acetate at alkaline pH
Hemoglobin EE
*Hemoglobin Electrophoresis
Hemoglobinopathies
Hemoglobin C
• Substitution of glutamic acid at 6th position of beta
chain
• Common in African-Americans
• Mild to moderate hemolysis
• Splenomegaly
• No vasoocclusive disease
• Smear
– Target cells in heterozygotes & homozygotes
– Crystals with homozygous patients only
– Hgb migrates with E at alkaline pH
• SC disease manifests …more problematic with
Hemoglobin CC
Hemoglobinopathies
Hemoglobin D
• Substitution of glutamine of glutamic acid on the
121 amino acid of the Beta-globin chain
– Most prevalent in India
– Heterozygotes are not anemic
– Homozygotes demonstrate a mild hemolytic anemia
• D migrates with S on at alkaline pH
electrophoresis and requires acid citrate agar to
differentiate the two
Hemoglobinopathies
Hemoglobin E
• Most Common in Thailand
• Migrates with C
• Mild hemolysis in homozygous form
• Target cells in peripheral blood
Hemoglobin E
*Microcytic Hypochromic
Anemia
*Hypochromic Mirocytic RBCs
Differential: Iron Def. vs. Thal.
*Thalassemia
• Abnormal production of globin chain proteins
• Gene mutations associated with quantitative
failure in chain production
• Diagnosis is based on changes in intracellular
levels of major hemoglobin types (normal-below)
• Hgb A = 97.5% = alpha (2) + beta (2)
• Hgb A2 = 2% = alpha (2) + delta (2)
• Hgb F = 1%= alpha (2) + gamma (2)
***Thalassemia
Alpha Thal
• 4 alpha genes
• Missing 1 to 4 genes
• Missing one alpha…silent carrier…normal
phenotype…no anemia & normal MCV
• **Missing 2 alphas
– *Mild anemia & decreased MCV
– *Alpha+/alpha-//alpha+alpha- African/American
– *Alpha-/alpha-//alpha+alpha+ Asian
• Inheritance of more severe form of alpha thal…Hgb H or
Hydrops fetalis
• Eg…Holy Land Patient
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Holy Land Patient
*Diagnosis Alpha Thal Minor
Missing 2 alphas
Hgb 11.5
MCV 70
RBC 5.85 million
Hgb A=97
*Hgb A2=2% …normal
Hgb F =1%
*Diagnosis by exclusion
**Thalassemia Minor vs. Iron
Deficient Anemia (Last 5)
*Thalassemia
Alpha Thal (Hemoglobin H)
• Missing 3 alpha genes
– Hemoglobin H disease
– Patient has 5-30% Hgb H (4 betas) on
electrophoresis
– Mild to moderate anemia (Hgb 7 to 10)f
– Reticulocytosis, microcytosis, hypochromia &
targeting….hemolysis….splenomegaly
Alpha Thalassemia **
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Thalassemia
Alpha Thal…Hydrops Fetalis ##
• Missing 4 alpha genes ##
• More common in Asians
• Stillborn
• Less common in Blacks
**Thalassemia
Beta Thal Minor
• Gene deletion(Beta 0) or mutation(Beta +)
• Heterozygous form
– **Increase in Hgb A2 to 4-7%
– Slight increase in Hgb F
– Confusion with iron deficiency
• Can lower A2 to normal
• Iron studies to exclude iron deficiency
**Globin Chain Development
A2 Increased in Beta Thal minor
Decreased in Beta Thal
Minor
Increased in
Beta Thal
Minor
Thalassemia ##
Beta Thal Major or Intermedia
• Severe microcytosis, targeting &
hypochromia
• Markedly increased Hgb F levels
• Beta 0 or Beta + mutation …homozygous ##
*Beta Thalassemia(minor)
***
##
Thalassemia Major
Thalassemia—Differential Dx
Alpha, Beta or Iron Deficiency
• Anemia, decreased MCV (75) in all 3
– Thalassemia
• RDW is not increased because uniform red cells
• Targets present because hemoglobin does not match
the membrane synthesis
• Beta Thalassemia…increased Hgb A2 **
– Iron deficiency
• Anisocytosis, poikilocytosis, pencil cells & increased
RDW (red cell distribution width)