Lecture 7 - hemoglobinopathies (final)

abnormality in Hb structure and function due to mutation in 1+ globin genes

1. type of amino acid substituted
2. location in globin chain
3. number of genes mutated

pt is homozygous (disease), clinical picture more severe than heterozygous (trait)

HB S
Hb C
Hb D-Punjab
Hb E

a2b2
severe hemolytic anemia, sickling

A2b2
mild hemolytic anemia

A2b2
no anemia

121 Gln (glutamine)

26 Lys

A2b2
mild Microcytic anemia

Hb M-Saskatoon
Hb Bethesda
Hb Kansas

Methemoglobinemia and cyanosis

A2b2 ^ (63Tyr)

Increased oxygen affinity

A2b2^(145His)

Decreased oxygen affinity

A2b2 ^ (102Thr)

1. Hb precipitates as Heinz bodies
2. Tetramer of normal chains

Hb hammersmith
Hb Zurich
Hb Ann Arbor

(Only in alpha thalassemia)
Hb H (beta4)
Hb Bart (gamma4)

a2b2^(6Glu->Val)glutamine->valine

Trait: AS
Disease: SS

Globally the sickle gene occurs highest in:
sub-Saharan Africa
Arab-India
Americas
Eurasia
Southeast Asia

Plasmodium falciparum. Sickle Cell Trait (SCT) gives protection against this parasite.

Selective destruction of RBCs containing parasites decreases number of malarial organisms and increases the time for immunity to develop

oxygenated and deoxygenated

when oxygen saturation decreases to <85%

sickling does not occur unless oxygen saturation is <40%

reversible
irreversible

Hb S containing RBCs that change shape in response to oxygen tension
responsible for vasocclusive crisis

sickle cells do not change their shape regardless of the change in O2 tension or degree of Hb polymerization
Seen on PBS as actual sickle cells

6 months after birth

1. vasocclusive 'painful' sequestration
2. chronic hemolytic, megaloblastic
3. aplastic

dropping of Hb to <6g/ dl (mostly in infants and young adults) could lead to autosplenectomy

due to folate depletion

common life-threatening hematologic complications usually associated with parvo B19 infection

polymerization
decreased deformability
sickle cell endothelial cell adherence
WBC/ platelet activation

acidosis, hypoxia, dehydration, infection/ fever,
extreme exposure to cold

type of HA
blood smear eval
retic count!!
MCV and RDW
cell counts
BM studies

increase nRBC/ polychromatic
MCH and MCV normal
sometimes RDW increase
leukocytosis (neutrophilia) & thrombocytosis

(305%) bc BM is responding properly

could signal aplastic crisis

tube solubility test
Hb electrophoresis

deoxygenated Hb S less soluble in solution, generating turbidity
(reducing agent sodium dithionite)

infants younger than 6 mo &
in low HCT

hyperlipidemia
too much blood added to the tube

separation of Hb molecules in an electric field primarily as a result of differences in total molecular charge

alkaline (pH 8.4)
acid (pH 6.2)

Hb molecules assume a negative charge and migrate toward the anode
(on cellulose acetate or recently agarose)

some Hb assume a negative charge and migrate toward the anode, whereas others are positively charged and migrate toward the cathode

A. A
B. F
C. S, D, G
D. A2, C, E, o

A. F
B. A, D, G, E, O
C. S
D. C

Hb S migrates with Hb D and Hb G

using citrate agar (acidic)
Hb D and G separate

they produce a negative result on Hb solubility test

Hb C migrate with Hb A2, Hb E, and Hb O

separates from A2, E, and O on acid electrophoresis

1. normal adult
2&3. SS
5&6. Sickle cell anemia recently transfused

presence of Hb A from the transfused RBCs in addition to Hb S on electrophoresis

heterozygous (Hb AS)
describes benign condition that does not affect mortality/ morbidity except under extreme exertion

normal RBC morphology (with a few target cells)
no abnormalities in leukocytes/ thrombocytes

positive

by detecting presence of Hb S and Hb A on hemoglobin electrophoresis or HPLC

approx 40% Hb S and approx 60% more Hb A;
Hb A2 normal or slight increase
Hb F level within reference

Hb C

by the structural formula a2B2^(6Glu→lys)
in which lysine replaces glutamic acid in position 6 of B chain

Hb C polymer structure differ under high oxygen tension;
Hb S polymers long/ thin, Hb C are short, thick crystals within RBCs

manifests as milder disease compared to SCD,
mild splenomegaly and hemolysis may be present
Vasoocclusion does not occur

asymptomatic

mild-moderate
normocytic normochromic in Hb CC

occasional micro/ hypo
marked increase in target cells
nRBCs

slightly to moderately high (2-3%)

NO Hb A present in CC
Hb C >90%
Hb F <7%
Hb A2 ~2%

60% Hb A
30% Hb C

Hb C migrates at the same position as Hb A2, E, & O-Arab

'bars of gold'

southeast Asia
highest incidence in Thailand

a2B2^(26Glu→Lys)

EE (disease): mild anemia with microcytes & target cells
AE (trait): asymptomatic

IDA, B-thal minor

because highest incidence in areas where malaria is present, it is though that P falciparum multiplies more slowly in Hb EE RBCs than Hb AE or Hb AA RBCs;
Mutation may give some protection against malaria

negative
must be confirmed using electrophoresis or HPLC

>90% Hb E
mild anemia (Hb 11-13 g/ dl)
low MCV (55-65 fl)
few-many target cells
normal retic

approx 25-30% Hb E
normal Hgb levels
MCV of 65 fl
target cells
slight erythrocytosis

Hb C, O, A2

Hb E separated from Hb C but it comigrates with Hb A & O

Hb SC

aa substitutions
ethnic distribution: 25% W Africa
1 in 833 births/ year in US

milder than SS, may cause vasoocclusion

mild normocytic, normochromic anemia
with many features associated with sickle cell anemia
Hb ~11-13 g/ dl
retic is 3-5%

few sickle cells
target cells
intraerythrocytic SC crystals

positive

Hb C and Hb S migrate in almost equal amts (45%) on alkaline electrophoresis
Hb F is normal

normal Hgb structure but the production amount changes

mutations in B gene cluster on chromosome 11;
results in B chain production

deletion of one or more α gene
affects a chain production

globin shortages
globin excesses

6 months to 1 year

during fetal life

no β chains are produced β0/ β0
does not produce Hb A (α2β2)

partial deficiency of β chains (ranging from 5-30%)
decrease in production of Hb A

minimal reductions in β chain production, mild or silent clinical states
(aka silent carrier)

no δ or β chains are produced
in homozygous δβ0/ δβ0, no Hb A or Hb A2 (α2δ2) is produced

deletion of either α1 or α2 globin gene on chr 16; results in decreased production of α chains from that chromosome
- α haplotype

deletion of both α1 or α2 globin gene on chr 16; results in no production of α chains from that chromosome
- - haplotype

β+/ β

β0/ β0

δβ0/ δβ0

βsilent/ β

asymptomatic; normal hematologic parameters

asymptomatic;
mild anemia
microcytic hypochromic

transfusion-dependent thalassemia,
severe anemia
microcytic hypochromic

non transfusion dependent
mild to mod anemia
microcytic hypochromic

one β gene mutated, the other one is normal

11-15 g/ dl in men
10-13 g/ dl in women
slight asymptomatic anemia

slightly increased, micro/ hypo
MCV<75 MCH<26
poik (targets, ellipto)
basophilic stippling

Hb A 92-95%
Hb A2 elevated (3.5% to 7.0%)
Hb F 1-5%

mild-mod erythroid hyperplasia with minimal ineffective erythropoiesis

homozygous

6 mo to 2 yrs

no Hb A
Hb F 95%

usually <7
but could be 2-4

high affinity for oxygen

poikilocytosis
elliptocytes, schistocytes, target cells, tear drop, spherocytes, hypochromic, microcytosis
basophilic stippling, nRBCs
(basically all morphology)

bone changes

normal αα/ αα
silent αα/ α-
α thal trait -α/-α or αα/--
Hb H -α/ --
Hb Barts/ hydrops fetalis --/ --

3 α genes deleted (--/ -α)
β chain tetramers form (β4)

10-40% of Hb Bart (y4)
w/ remainder being Hb F and Hb A

Hb H replaces most of Hb Bart
Hb H is 1-40% with reduced amt of Hb A2,
traces of Hb Bart, and remainder Hb A

mild-mod chronic hemolytic anemia
Hb 7-10 g/ dl with retic 3-10%

Hb H inclusions (brilliant cresyl blue)
golf ball appearance

homozygous α0-thalassemia (--/ --)
results in no α chain production

without intrauterine transfusion, fetus becomes severely anemia, which leads to cardiac failure and edema in fetal subcutaneous tissues

fewer RBC, RBC inclusions

HISTORY & physical exam
(bc thalassemia belt where high incidence of thal)

hypo/ micro
MCV MCH MCHC Low
RDW normal (thal minor)
RDW high (thal major)
OF (not helpful, usually low in minor bc target cells, resistant to lysis)
Hb electrophoresis

1. Normal
2. Sickle trait
3. Sickle anemia

thal has hx in family (IDA happens regardless)
RBC/ MCV < 13 favors thal minor
RBC/ MCV > 13 favors IDA
IDA has FEP or ZPP
Iron studies