Microcytic/Macrocytic Anemia/Iron: Weir Flashcards
Function of Hepcidin in healthy body?
- Hepcidin is the main regulator of iron absorption, transport, and storage.
- It downregulates ferroportin, the key “Gateway” protein facilitating dietary iron absorption and iron stores’ release.
- It’s levels are normally dictated by transferrin saturation levels.
average dietary intake of iron/day?
1mg in, and 1 mg out in most patients
pregnant and menstruating women tend to lose additional iron
role of transferrin in normal body function?
binds free iron released into the blood plasma (either from dietary absorption or storage release)
iron must be in ferric form to bind to transferrin.
What is DMT-1?
The active transporter of iron, that facilitates dietary iron absorption
in the ferrous (fe2+) form, iron is transported from the gut lumen to enterocyte cells.
Duodenal Cytochrome B fx and location
he reductase enzyme which catalyzes the reduction of Fe3+ to Fe2+ in the process of iron absorption in the duodenum; aka as ferrireductase
Ferroportin
the second transporter that facilitates absorption of iron, acting as a gate keeper between basement membrane of enterocyte and the plasma blood celll
Hephaestin
a ferrioxidase enzyme, that reconverts Fe2+ to Fe3+ so that the iron can bind transferrin once dumped into the blood stream
What promotes iron absorption by enhancing the reduction of fe3+ to 2+
vitamin C (it is a necessary cofactor )
Mech. of Action of Hepcidin in Anemia of Chronic Inflammation
Hepcidin spikes because inflamm. cytokines like IL-6 stimulate the liver to produces more hepcidin (it’s an acute phase reaction).
increased hepcidin–>decreased ferroportin–>so your storage macrophages in spleen, liver, + bonemarrow are stufffffffed (with ferritin)
Mech of Action of Hepcidin in Hypoxia
Hypoxia means the release of Hypoxia Inducible Factor (HIF), which decreases hepcidin levels–>increases ferroportin–>increases serum iron levels
(makes sense…you need to mobilize iron so that you can make more RBC’s to get more oxygen carrying capacity)
two other random mediators of hepcidin inhibition?
TWSG1 and GDF-15
Pathogenesis of Hereditary Hematochromatosis/Mechanism of Action of Hepcidin in Hematochromatosis
mutation in HFE gene/this actually causes a decreased levels of hepcidin–>increased ferroportin and thus EXCESS duodenal iron absorption/macrophage release of iron
(phenotypic presentation of disease is more common in men, because women tend to lose iron more than men thanks to menstruation and pregnancy)
Erythropoeitin’s impact on hepcidin levels
inhibits hepcidin, again..makes sense.. you need more iron mobilization to make new red blood cells
Relationship between Transferrin Saturation and Hepcidin
In every case of anemia EXCEPT anemia of chronic inflammation, hepcidin levels are pinned to transferrin saturation levels. When you have increased transferrin saturation, you have increased hepcidin. When you have decreased transferrin saturation, you have decreased hepcidin.
In Anemia of Chronic Inflammation, your hepcidin levels are increased (thanks to IL-6), but this creates decreased iron, and so your transferrin saturation levels are actually decreased
Mechanism of Action of Hepcidin in Iron Deficiency Anemia
Decreased iron will lead to decreased hepcidin, and thus increased ferroportin
Mechanism of Action of Transferrin in Hematochromatosis
Transferrin levels go down (TIBC)
transferrin saturation is at it’s max (since you have wayyyyy too much iron in the blood)
Mechanism of Action of Transferrin in Iron Deficiency Anemia
Increased transferrin levels (TIBC), decreased transferrin saturation (not enough iron, elevated TIBC)
transferrin saturation calculation
serum iron divided by transferrin iron binding capacity (TIBC…which represents total amount of transferrin)
Three clinical signs of iron deficiency
- Koilonchyia (Spooning of Nails)
- Angular Cheilosis (ulceration of corners of mouth)
- Glossitis (glossy, atrophied tongue, loss of papillae)
FOR IRON DEFICIENCY ANEMIA
Ferritin Conc
Serum Iron Conc
TIBC Level
Transferrin Saturation Level
MCV (which determines macro or microcytic btw)
Serum Soluble Transfer Receptors (used to distinguish iron def anemia and chronic inflammation anemia)
Decreased Ferritin Decreased Iron Elevated TIBC Decreased Transferrin Saturation low MCV Elevated Serum Soluble Transfer Receptors
FOR ANEMIA OF CHRONIC DISEASE
Ferritin Conc
Serum Iron Conc
TIBC Level
Transferrin Saturation Level
MCV (which determines macro or microcytic anemia btw)
Serum Soluble Transfer Receptors (used to distinguish iron def anemia and chronic inflammation anemia)
Elevated Ferritin (but that's also because ferritin is an acute phase reactant, not bc of anemia, so you need to look at serum soluble transfer receptors before deciding between anemia of chronic disease and iron deficiency) Decreased Iron Decreased TIBC Elevated or Same Transferrin Saturation MCV: low or normal normal serum transfer receptor lvls
THALASSEMIA Ferritin Conc Serum Iron Conc TIBC Level Transferrin Saturation Level MCV (which determines macro or microcytic anemia btw)
everything is normal except
MCV which is pretty low
this makes sense bc hemoglobin production is not impaired bc of heme production…
globulin production is the thing that’s impaired
Normal Levels for Transferrin Saturation
> 20% (it’s actually about 33%ish because only one third of TIBC is occupied by iron)
Transferrin Saturation in iron deficiency anemia
<10%
Red Cell description in Iron Deficiency Anemia
HYPOCHROMIA: Central pallor (from lack of hemoglobin) that takes up about half of the cell diameter (as opposed to normal which is 1/3rd central pallor)
MICROCYTIC: Red blood cell is normally the size of a lymphocyte nucleus…not in microcytosis though.
FOR IRON OVERLOAD (as seen in Hemochromatosis)
Ferritin Conc Serum Iron Conc TIBC Level Transferrin Saturation Level MCV (which determines macro or microcytic anemia btw) )
Elevated Ferritin Increased Iron Decreased TIBC Maximum Transferrin Saturation MCV: elevated
What stain is used to stain iron in blood smears?
Prussian Blue
Clinical Features of Hemochromatosis
- Hyper pigmentation (bronze appearance)
- Hepatomegaly/Hepatic Cirrhosis
- Diabetes Mellitus
Increases susceptibility to congestive heart failure (iron gets trapped up in the heart)
Hemochromatosis epidemiology
Autosomal Dom or Recessive?
Northern Europe (5 in 1000 ppl are homozygous for mutated HFE gene) Men more likely to show phenotype
Autosomal Recessive Disorder
Penetrance is variable
What is the specific mutation within HFE that causes Hemochromatosis 90% of the time?
Type 1 (with C282Y mutation)
Microscopic indications of hemochromatosis
lots of hemosiderin (golden brown deposits), which is a storage complex of iron
Therapy for Hemochromatosis?
Phlebotomy
Drain out blood until the ferritin level gets below 50
At that point, your normal iron regulating mechanisms kick in, and you start sucking out iron from the liver, spleen, bone marrow, etc.
Definition of Sideroblastic Anemia
any anemia where iron is trapped in the mitochondria of precursor forms of red blood cells (bc mature RBC’s don’t have MT stupid)
Microscopic indications of Sideroblastic Anemia
Ring Sideroblasts: blue perinuclear ring of iron granules in red cell precursors
Causes of Sideroblastic Anemia (4)
lead poisoning
defect in ALA Synthase enzyme
myelodysplasia
Tuberculosis therapy
One clinical finding of lead poisoning
“Lead Line” in the gums
Microscopic indication of lead poisoning or sideroblastic anemia sometimes
basophillic stippling (little blue dots all over mature red blood cell) from precipitated RNA
Causes of Macrocytosis OTHER THAN megaloblastic anemia (4)
alcohol, liver disease, hypothyroidism, and myelodysplasia
you will NOT see anemia, just enlarged RBCS
Dietary way to resolve folate deficiency
eat more uncooked veggies
two main types of megaloblastic anemias
B12 and Folate Deficiencies
pathogenesis for pernicious anemia
autoimmune disease where you don’t have Intrinsic Factor (because you have antibodies against parietal cells in 90% of the cases) (in 50% of the cases you have antibodies to IF), so there is nothing to bind B12 in the jejunum and carry it to the ileum (where B12 absorption takes place)
2 main causes of b12 deficiency
inadequate diet and malabsorption (that includes pernicious anemia among a bunch of other things…look at blue chart in the notes)
site of genetic mutation most common to sideroblastic anemia
ALA Synthase enzyme
defect in ALAS2, which is involved in the first step of heme synthesis. Although X-linked, approximately one third of patients are women due to skewed X-inactivation.
where does b12 get absorbed
the illium
epidemiology of Pernicious Anemia
all races, mostly northern european, usually age>60
in black women, increased incidence under age of 50
clinical finding of pernicious anemia
atrophic gastritis, sometimes increased incidence of gastric cancer
test for pernicious anemia
indirect immunofluorescent test for anti-parietal cell antibody (sensitive but not specific…so positive results are seen in other diseases besides just pernicious anemia)
can be done in combo with immunofluorescent test for anti-intrinsic factor antibody, which is specific but not sensitive, so only really seen in pernicious anemia, but not all cases of pernicious anemia will have it
clinical indicators (2) of B12 deficiency
pallor
red, beefy, painful tongue
microscopic indicators of megaloblastic anemia
- megalovalocytes (big, oval rbcs)
- hypersegmented neutrophils (5-6 lobes or more)
- white, open lacy chromatin with asynchronous maturation of nucleus-looks like “blastic” appearance of cells.
why does B12 cause neurological issues
inability to produce methionine, which plays a role in synthesis of sphingomyelin (key component of myelin sheath).
types of neurological issues seen in B12 deficiency
Early:
Paresthesia of hands and feet
Somnolence (sleepiness) and dementia
Decreased vibratory and proprioception
Late:
Spastic paralysis from demyelination of dorsal and lateral columns Not reversible
“Combined system disease”
treatment for b12 deficiency
1000 micrograms of B12 daily (intramuscularly) for 1 week, then weekly for 4 weeks then monthly for life.
oral B12 2000 micrograms daily once stores replete, in place of IM admin
DO NOT GIVE FOLATE, can worsen neurological damage
prognosis of b12 deficiency after treatment plan?
Bone marrow resolves in 2-3 days
Hgb will become normal in 1-2 months
mechanism of action of B12
facilitates the following rxn:
methyl THF and homocysteine–>methionine and THF
THF is in turn necessary to convert to 5, 10 methylene THF poly glutamate, which is necessary for dUMP–>dTMP
mechanism of action of folate
dietary folate is involved in biochemical reactions involving single carbon transfers. specifcally folate–>methyl THF
4 causes of iron deficiency
insufficient dietary intake
malabsorption
excessive demand (infancy or pregnancy)
chronic blood loss (GI bleed, menstruation)
