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Hemoglobin
Heme = Fe++ + Porphyrin Ring
+
Globin
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Hemoglobin
Function Conjugated protein
for transport of O2 &
CO2
&
Buffer (O2
Dissociation Curve)
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Basic Structure
How many? subunits:
How many? iron-containing tetrapyrroleheme rings
How many? polypeptide
globin chains ? identical alpha chains
? identical non-alphachains
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Basic Structure
Each chain arrangedin -helix w/ 8individual helicalsegments (labeled A -H)
Each globin moleculehas both hydrophobic& hydrophilic areas
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Basic Structure
Fe-containing heme ring w/inhydrophobic region of globin -Heme Pocket
Hydrophobic nature protectsFe residue from oxidation
Each Fe at center of hemeresidue held in place & kept
active (Fe++) by 2 histidineresidues
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Hemoglobin Chemistry
O2 binds to heme (Iron)
97% carried this way
CO2 binds to globin
20% bound
80% free in plasma
CO2 causes acidity in
plasma, effects the pH
balance of the blood
Blood can carry both at
one time different
binding
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Basic Structure
Each globin (141 aa)
All non- chains (146
aa) W/ considerable
structural homology
among non-alpha
chains
Full saturation: 1 gm
Hgb holds 1.34 mL of
O2
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Normal Hgb:
Hgb A1
95 - 98% (adult)
15 - 40% at birth
predominates at 6 12mons
Hgb F
< 2% (adult)
1 - 0.8% (3 y/o)
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Hgb derivatives (Heme changes)
Oxyhgb (bright red) vs Reduced hgb (purple red)
Maintained by methemoglobin- cytochrom C
reductase 575 nm
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Hgb derivatives (Heme changes)
Carboxyhgb (cherry
pink)
200 X affinity vs O2 Collect in citrate
Test: ammonia + blood
(25% COHgb)
CO poisoning occur atlevels of 20-30%
540 nm
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Heavy smokers: Smokers: 1-10%
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Hgb derivatives (Heme changes)
Methgb (0.5% normal in
blood)
Fe++ Fe+++ brown
No O2 binding cyanotic
Induced by oxidizing
agents (nitrates, nitrites,
quinones, chlorates)
G-6-PD deficiency
525 nm
Sulfhgb (0- 2.2% normal
in blood)
Sulfa drugs (sulfonamides);
aromatic aminestrinitrotoluene
Irreversible binding RES
Myoglobins
Porphyrins
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Iron Metabolism
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Body Iron Distribution and StorageDietary iron
Utilization Utilization
Duodenum
(average, 1 - 2 mg
per day)
Muscle
(myoglobin)
(300 mg)
Liver
(1,000 mg)
Bone
marrow
(300 mg)Circulating
erythrocytes
(hemoglobin)
(1,800 mg)
Reticuloendothelial
macrophages
(600 mg)
Sloughed mucosal cellsDesquamation/Menstruation
Other blood loss(average, 1 - 2 mg per day)
Storage
iron
Plasma
transferrin
(3 mg)
Iron loss
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Major Iron Compartments
Metabolic:
Hgb 1800 - 2500 mg
Myoglobin 300 - 500 mg
Storage:
Iron storage 0 - 1000 mg
Transit:
Serum iron 3 mg
Total 3000 - 4000 mg
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Red cell indices
Hemoglobin (gm\dl): 13.5- 17 M
12- 15 F
Hematocrit (Vol%): Volume of RBCs /Total blood
39- 49 % M
33- 43% F
RBCs ct (106/ul): 4.3- 5.9 M3.5- 5 F
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Iron Deficiency
Anemia (IDA)
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Clinical
Features: General features of
Anemia
Pallor, Weakness,Lethargy
Breathlessness onexertion
Palpitationsheart failurepedal edema
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Clinical
Features: Special features in
IDA:
Angular cheilitis,atrophic glossitis,
Esophagealatrophy/web
dysphagia,Koilonychia, brittle
nails, gastricatrophy
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PBS: Response to Iron Tx
Dimorphic blood film
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Other LAB Tests:
DEC SERUM Fe
DEC SERUM FERRITIN Most useful, cost effective test of Fe stores
> 100 ng/ml r/o IDA Except in acute hepatitis or liver necrosis butnot chronic liver dse (elevated- release of Fe stores)
Falsely elevated- disseminated TB & Hodgkin's disease
INC TIBC (high specificity- near 100% but poorsensitivity- < 30%)
BM: ASYNCHRONOUS RBC-POIESIS
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Hemochromatosis: Overview
Def: Xss accumulation of Fe w/ organ damage
Iron arithmetic: Normal total body pool: 2-5 gm
Hgb (2 gm)
Storage: ferritin & hemosiderin (0.5 - 1 gm)
Myoglobin (0.3 gm)
Normal liver storage: 0.5 gm
Hemochromatosis: Total body Fe > 50 gm
At least 1/3 is stored in liver
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Hemochromatosis: classification
Genetic (hereditary) vs secondary (acquired)
Secondary causes iron overload: Parenteral iron overload (transfusions, iron-dextran
injections)
Ineffective erythropoiesis hemolytic anemias (mostcommon secondary cause)
Increased oral intake (Bantu siderosis)Congenital atransferrinemia
Chronic liver disease (mostly alcoholic)
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Genetic Hemochromatosis
Homozygous recessive
HFE gene on chr 6p (near HLA gene locus)
MC mutation in HFE: tyrosine substituted forcysteine at aa 282 (C282Y)
Gene frequency: 6% northern European whites;homozygosity 0.45% (1 in 220)
M: F = 6:1
Males show disease earlier (no menses)
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Hereditary Hemochromatosis:
pathogenesis
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Genetic Hemochromatosis:
Pathology Deposition hemosiderin
in multiple organs (browngranules of aggregatedferritin):
Liver & pancreas (mostsevere)
Myocardium
Pituitary, adrenal, thyroid,parathyroid glands
Joints (synovitis) and skin
Testes (atrophy)
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Hemochromatosis
Genetic dse
Excess amounts of
iron Arthritis, cirrhosis,
DM, heart failure,
HCC
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Hemochromatosis: Clinical Dx
Signs:Abdominal pain
Hepatomegaly
Skin pigmentation(brown-gray)
DM
Cardiac dysfunction
Arthritis
Hypogonadism
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Hemochromatosis: Clinical Dx
Diagnostic tools:
Markedly elevated serum ferritin (best screening test)
HFE gene molecular analysis Liver biopsy w/ quantitative Fe analysis
Normal: < 1,000 ug Fe/gm
Hemochromatosis: > 10,000 ug Fe/gm
Evaluate for secondary causes (vs. genetic)
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Anemia of Chronic
Disease: ACD
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ACD - ETIOLOGY: ANY
CHRONIC DSE Inflammatory:
Temporal arteritis
(may be a presenting
sign)
Rheumatoid arthritis
Cancer
Non-inflammatory:
CHF
COPD DM
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ACD
Infections: TB, SBE, Osteomyelitis
Chronic UTI or PN
Fungal
Malignancy: Mets
Leukemia
Lymphoma
Myeloma
Chronic inflammatorydisorders: RA
SLE Sarcoid
Collagen Vascular Dse
Polymyalgia Rheumatica
Chronic Hepatitis
Decubitus ulcer
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ACDDefect
Storage Iron
IL-1TNF IFN
Erythroid Precursors
(dec responsiveness to EPO)
BM Storage
Iron (Blue)
Fe SEQUESTRATION IN BM HISTIOCYTES
w/ defective Fe utilization & shorten RBC survival
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ACD - LAB DX:
INC. ESR
INC. HAPTOGLOBIN
Dec serum Fe
Dec TIBC
BM: Inc BM Fe stores w/ dec sideroblasts
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IDANormal
ACD
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Sample question #1
ACD is due to inadequate production of, orpoor response to, which one of the
following?
A. Iron
B. FolateC. Erythropoietin
D. Ferritin
E. HemosiderinAFP, Nov. 15, 2000
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Heme Synthesis
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Porphyrin Synthesis
& Structure
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Heme Synthesis
Glycine & Succinyl Co-A-amino
levulinic acid (-ALA)
The rate-limiting step in heme synthesis-intra-mitochondrial ALA- synthase
-ALA travels to cytoplasm; converted toPBG, a monopyrrole
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Heme Synthesis
PBG (monopyrrole) Protoporphyrin IX
(biologically active tetrapyrrole)
Fe inserted into tetrapyrrole ring in mitochondria
Heme synthesis:
Stimulated by Fe
Repressed when Fe is inadequate (IDA)
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Sideroblastic
Anemia
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SIDEROBLASTIC A. -
MECHANISM: Defective prdn of heme under- hgb
erythroid precursors w/ microcytosis
REFRACTORY A. (RESISTANT TO TX) INEFFECTIVE ERYTHROPOIESIS
(ANEMIA W/ HYPERPLASTIC BM)
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SIDEROBLASTIC A - ETIOLOGY
& Mechanism: HEREDITARY (X LINKED/ AR)
HEPATOSPLEENOMEGALY;THROMBOEMBOLISM
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SIDEROBLASTIC A - ETIOLOGY
& Mechanism:ACQUIRED:
IDIOPATHIC
NEUTROPENIA W/ PELGER HUET CELLS
PRONE TO Fe OVERLOAD; TE
10% DEVELOP AML
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SIDEROBLASTIC A - ETIOLOGY
& Mechanism: ACQUIRED:
DRUG INDUCEDALCOHOL- FOLATE DEF. + MALNUtrition
INH- VIT. B6 METABOLISMCHLORAMPHENICOL- MITOCHONDRIAL
INHIBITION
LEAD- HEME PATHWAY
Zinc, cycloserine, plavix
DISEASE ASSO. (THYROID; CA; LYMPHOMA;MM; RA)
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Sideroblastic A Lab Dx:
PBS: Papenheimer
Bodies; Basophilic
stippling in Pb
poisoning; Dimorphic(macrocytic + intensely
microcytic RBCs) in
patient w/ acquired
sideroblastic a;anisopoikilocytosis;
Target cells
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Sideroblastic A Lab Dx:
Serum Fe: Inc
Stigmata of a myelodysplastic syndrome
BM: Ringed sideroblasts on BM Fe stain;inc hemosiderin
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Porphyria cutanea tarda
Etiology:
Uroporphyrinogen decarboxylase def
Anti HC Ab
S/S:
Cutaneous photosensitivity
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Porphyria cutanea tarda
Features:
Portal inflam w/
cirrhosis
HCC
Inc hepatic Fe
Inc urinary
uroporphyrin
Lab tests:
Inc urine uroporphyrin
Inc aminotransferase
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Acute intermittent porphyria
AD w/ incomplete penetrance (other familymembers w/ the condition maybeasymptomatic)
Drugs & alcohol induced (P450 enzymeinducers)
Acute attack: urine turns dark on standing
(high ALA & PBG levels). Levels remainmoderately raised between attacks
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Variegate porphyria
AD disorder
Features: Cutaneous fragility &
photosensitivityAcute neurological attacks common
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Globin Synthesis
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Location of the Globin Genes
Duplication of genes
for:
Globin
Globin (G & A) *
G & A differ from
one another only at
position 136 (glycine
& alanine
respectively)
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Globin chain synthesis
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Globin chain synthesis cluster - chromosome 16
b cluster - chromosome 11
z2e2 Gower 1
z22 Portland Embryonic
2e2 Gower II
22 F Fetal 95%
12
e G bA
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Ferritin
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Iron deficiency
Reduced
HB electrophoresis Anemia of Chronic Disease
Normal
Bone marrow
Ringed sideroblasts
Increased
Furtherinvestigations to
find the cause are
necessary
If HB
electrophoresis isnormal then do
alpha gene mapping
HypochromiaMicrocytic
Note: Anisocyosis:
RDW
poikilocytes
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WAKAS!!!