Anaemia:
Anemia ( meaning lack of blood) is a decrease in
number of red blood cells (RBCs) or less than the
normal quantity of hemoglobin in the blood.
However, it can include decreased oxygen-
binding ability of each hemoglobin molecule due
to deformity or lack in numerical development as
in some other types of hemoglobin deficiency.
The normal level of hemoglobin is generally
different in males and females. For men, anemia is
typically defined as hemoglobin level of less than
13.5 gram/100ml and in women as hemoglobin of
less than 12.0 gram/100ml.
These definitions may vary slightly depending on
the source and the laboratory reference used
What causes anemia
•Any process that can disrupt the normal life span
of a red blood cell may cause anemia. Normal life
span of a red blood cell is typically around 120
days. Red blood cells are made in the bone
marrow.
•Anemia is caused essentially through two basic
pathways. Anemia is either caused:
by a decrease in production of red blood cell or
hemoglobin, or
by a loss or destruction of blood.
WHO's Hemoglobin thresholds used to
define anemia
(1 g/dL = 0.6206 mmol/L)
Age or gender
group
Hb threshold (g/dl)
Hb threshold
(mmol/l)
Children (0.5–5.0
yrs)
11.0 6.8
Children (5–12 yrs)11.5 7.1
Teens (12–15 yrs)12.0 7.4
Women, non-
pregnant (>15yrs)
12.0 7.4
Women, pregnant 11.0 6.8
Men (>15yrs) 13.0 8.1
Peripheral blood smear microscopy of
a patient with iron-deficiency anemia.
Classification:
1. Microcytic :
Microcytic anemia is primarily a result of hemoglobin synthesis
failure/insufficiency, which could be caused by several etiologies:
•Heme synthesis defect
–Iron deficiency anemia
–Anemia of chronic disease (more commonly presenting as normocytic
anemia)
•Globin synthesis defect
–alpha-, and beta-thalassemia
–HbE syndrome
–HbC syndrome
–and various other unstable hemoglobin diseases
•Sideroblastic defect
–Hereditary sideroblastic anemia
–Acquired sideroblastic anemia, including lead toxicity
–Reversible sideroblastic anemia
2. Macrocytic :
•Megaloblastic anemia, the most common cause of macrocytic
anemia, is due to a deficiency of either vitamin B
12
, folic acid (or
both). Deficiency in folate and/or vitamin B
12 can be due either
to inadequate intake or insufficient absorption. Folate deficiency
normally does not produce neurological symptoms, while
B
12 deficiency does.
Pernicious anemia is caused by a lack of intrinsic factor.
Intrinsic factor is required to absorb vitamin B
12
from food. A
lack of intrinsic factor may arise from an autoimmune condition
targeting the parietal cells (atrophic gastritis) that
produce intrinsic factor or against intrinsic factor itself. These
lead to poor absorption of vitamin B
12
.
Macrocytic anemia can also be caused by removal of the
functional portion of the stomach, such as during gastric
bypass surgery, leading to reduced vitamin B
12
/folate absorption.
Therefore one must always be aware of anemia following this
procedure.
Hypothyroidism
Alcoholism commonly causes a macrocytosis, although not
specifically anemia. Other types of Liver Disease can also cause
macrocytosis.
Methotrexate, zidovudine, and other drugs that inhibit DNA
replication.
Macrocytic anemia can be further divided into "megaloblastic
anemia" or "non-megaloblastic macrocytic anemia". The cause of
megaloblastic anemia is primarily a failure of DNA synthesis with
preserved RNA synthesis, which result in restricted cell division of the
progenitor cells. The megaloblastic anemias often present with
neutrophil hypersegmentation (6–10 lobes). The non-megaloblastic
macrocytic anemias have different etiologies (i.e. there is unimpaired
DNA globin synthesis,) which occur, for example in alcoholism.
Normocytic:
Normocytic anemia:
Normocytic anemia occurs when the overall
hemoglobin levels are always decreased, but the
red blood cell size (Mean corpuscular volume)
remains normal. Causes include:
Acute blood loss
Anemia of chronic disease
Aplastic anemia (bone marrow failure)
Hemolytic anemia
Dimorphic:
When two causes of anemia act simultaneously,
e.g., macrocytic hypochromic, due
to hookworm infestation leading to deficiency
of both iron and vitamin B
12
or folic acid or
following a blood transfusion more than one
abnormality of red cell indices may be seen.
Evidence for multiple causes appears with an
elevated RBC distribution width (RDW), which
suggests a wider-than-normal range of red cell
sizes.
Heinz body anemia:
Heinz bodies form in the cytoplasm of RBCs and
appear like small dark dots under the microscope.
There are many causes of Heinz body anemia,
and some forms can be drug induced.
It is triggered in cats by
eating onionsor acetaminophen (paracetamol). It
can be triggered in dogs by ingesting onions
or zinc, and in horses by ingesting dry red
maple leaves
Refractory anemia :
Refractory anemia is an anemia which does
not respond to treatment. It is often seen
secondary to myelodysplastic syndromes.
Iron deficiency anemia may also be refractory
as a clinical manifestation of gastrointestinal
problems which disrupt iron metabolism
Iron regulation
and metabolism
•Body iron content – 3-4g
–Hb, iron containing proteins, bound to Tf,
storage (ferritin, haemosiderin).
•Iron homeostasis is regulated strictly at
level of intestinal absorption.
Regulation of iron balance
•Haem diet – very readily absorbed via haem
carrier protein 1 (apical bruish border membrane
of duodenal enterocytes) i.e. higher
bioavailability.
•Remainder of dietary iron poorly absorbed (10%).
–Ascorbic acid enhances absorption of non-animal
sources of iron; tannates inhibit absorption.
•Fe2+ better absorbed cf. Fe3+.
Intestinal iron absorption
•Fe3+ freed from food binding sites in
stomach, binds to mucin, travels to
duodenum and small bowel.
–Haem iron - carrier protein (endocytosis).
–Fe3+ - attachment to an integrin.
–Fe2+ - intestinal transporter DMT1.
Intestinal iron absorption
•Iron then enters cytosol, binds to cytosolic
low molecular weight iron carriers and
proteins e.g. Mobilferrin (shuttles iron with
help of ATP) to basolateral membrane
•Export from basolateral membrane via
duodenal iron exporter.
Intestinal iron absorption
•Upon release into circulation, re-oxidised to
Fe3+, loaded onto transferrin.
–Site of influence of HFE gene product, +/-
caeruloplasmin (known ferroxidase).
Iron transport
•Iron absorption regulated by many stimuli –
–Iron stores.
–Degree of erythropoiesis (increased with
increased erythropoiesis, reticulocytosis).
–Ineffective erythropoiesis.
–Mobilferrin – mechanism of loss in iron replete
state.
Iron regulation
Iron Absorption Procedure
Iron absorption in the human body takes place through the
digestive tract, most importantly the small intestine. The
remaining organs of the digestive system always contribute their
bit to breaking down of food matter. However, the important part
comes when the iron from the food source gets assimilated into the
blood flow and into the hemoglobin. This process is aptly termed
as the 'absorption' of iron. In human body, the small intestine is
classified into different parts. The duodenum is the first part and is
the place of iron absorption. This process of absorption is initiated
by a class of cells that is termed as enterocytes. These cells are
present in the inner glycocalyx surface of the duodenum, of the
small intestine. The glycocalyx, is an extracellular polymeric
surface that is secreted by the cells themselves.
Moving on to the chemical procedure of the iron absorption, it
must be noted that irons that are a part of the protein, are usually
absorbed by the body. This 'absorbable' iron containing protein is
often referred to as the heme protein. The ferrous form of this
protein is chemically represented as Fe
2+
. Not all dietary irons are
in this form, and some of them have to be reduced down from Fe
3+
.
This function is conducted at the 'brush border', where a ferric
reductase enzyme (a type of enzyme), duodenal cytochrome B,
reduce it down to Fe
2+
. The process of conversion finishes here and
a protein by the name DMT1, which is also known as divalent
metal transporter 1, transports the iron into the cell. There are some
very complex procedures that are involved in later stages where the
iron optimizes the oxygen carrying capacity of the hemoglobin.
IRON ABSORPTION
Favored by
•Dietary factors:
Increased Haem iron
Increased animal iron
Ferrous iron salts
•Luminal factors:
Acid pH (e.g. gastric HCl)
Low molecular weight soluble
chelates
(e.g. Vit. C, sugars, amino acids)
•Ligand in meat (unidentified)
•Systemic factors:
Iron deficiency
Increased erythropoiesis
Ineffective erythropoiesis
Pregnancy
Hypoxia
Reduced by
Decreased haem iron
Decreased animal iron
Ferric iron salts
Alkalis (e.g. pancreatic
secretions)
Insoluble iron complexes (e.g.
phytates, tannates in tea,
bran)
Iron overload
Decreased erythropoiesis
Inflamatory disorders
•Transferrin and TfR.
•Ferritin.
•Iron responsive element-binding protein (IRE-BP) aka iron
regulatory protein/factor (IRP/IRF).
•HFE.
•Divalent metal transporter (DMT1, Nramp2,
DCT1,Slc11a) – duodenal iron transporter.
•Ferroportin and hephaestin, iron export proteins.
•Hepcidin.
Role of specific proteins
•Encoded on long arm of chromosome 3.
•Half life 8 days.
•Hepatic synthesis.
•Complete lack incompatible with life
(hypotransferrinaemia).
Transferrin (Tf)
•Also on long arm of chromosome 3.
homodimeric transmembrane protein.
–Found in most cells. Most dense on erythroid
precursors, hepatocytes, placental cells.
–Restricted expression: both TfR1 and TfR2
present at high levels in hepatocytes, epithelial
cells of small intestine including duodenal crypt
cells.
Transferrin receptor (TfR)
•Each TfR binds 2 diferric Tf molecules.
Uptake by clustering on clathrin coated pits,
then endocytosed.
•Iron off-loaded in acidified vacuoles,
apotransferrin-TfR complex recycled to cell
surface, apo-Tf then released back into
circulation.
Transferrin receptor (TfR)
•Cellular storage protein for iron.
•L and H chains (chromosome 19, 11).
•Synthesis controlled at 2 levels –
–DNA transcription via its promotor.
–mRNA translation via interactions with iron
regulatory proteins.
•Acute phase reactant.
Ferritin
Ferritin in erythroid precursors may be of special
importance in haem synthesis especially at
beginning of Hb accumulation, when Tf-TfR
pathway still in sufficient.
When ferritin accumulates, it aggregates,
proteolyzed by lysosomal enzymes, , then converted
to iron-rich, poorly characterised haemosiderin,
which releases iron slowly.
M-ferritin – present in mitochondria. Expression
correlated with tissues that have high mitochondrial
number, rather than those involved in iron storage.
Ferritin
•Sensing iron-regulatory proteins modulate
synthesis of TfR, ferritin, DMT1.
–IRP1 and IRP2 – cytosolic RNA binding
proteins. Bind to iron-responsive elements
located in 5’ or 3’ untranslated regions of
specific mRNAs encoding ferritin, TfR, DMT1
and (in erythroid cells) eALAS.
Iron-regulatory proteins and iron-
responsive element binding protein
Expression in GIT limited to cells in deep crypts in
proximity to site of iron absorption.
HFE protein associated with TfR, acts to modulate
uptake of Tf-bound iron into crypt cells.
Along with hepcidin, acts as iron sensor.
Hereditary haemochromatosis with HFE gene
mutation - inability to bind beta 2-microglobulin,
impaired cellular trafficking, reduced incorporation
into the cell membrane, reduced association with
TfR1.
HFE protein
•Divalent metal transporter protein – iron
transporter (also Pb, Zn, Cu).
•Widely expressed, esp. in proximal
duodenum.
•Isoform containing iron responsive element
(Nramp2 isoform I) specifically upregulated
in iron deficiency, greatest expression at
brush border of apical pole of enterocytes in
apical 2/3 of villi.
Duodenal iron transporter
•Increased body iron stores – enhanced uptake
of iron from circulation into crypt cells.
•Increasing intracellular iron into crypt cells,
differentiating enterocytes migrating up to
villus tip downregulate iron transporter
DMT1, reducing absorption of dietary iron
from gut.
•Inverse relationship between ferritin levels in
serum, and DMT1 levels in duodenal cells.
Duodenal iron transporter
•Transporting iron from basolateral
membrane of enterocytes to circulation;
from macrophage (from effete RBCs) into
circulation for formation of new Hb.
–Ferroportin.
–Hephaestin.
Iron exporters
•Ferroportin-1 in basal portion of placental
syncytiotrophoblasts, basolateral surface of
duodenal enterocytes, macrophages,
hepatocytes.
•Upregulated by amount of available iron,
downregulated through interaction with
hepcidin.
Ferroportin
•Homology to caeruloplasmin.
•Link between iron deficiency and copper
deficiency – administration of copper
facilitates progress of iron from tissue(s)
into circulation.
Hephaestin
•SFT-mediated transport has properties
defined for Tf-independent iron uptake,
transporting iron across lipid bilayer.
Process dependent on Cu.
•Has ferrireductase activity.
•Cytosolic localisation in recycling
endosomes, stimulates Tf bound iron
assimilation.
Stimulator of iron transport
(SFT)
•25 aa peptide hormone.
•Chromosome 19.
•Synthesized by hepatocyes. Intrinsic
antimicrobial activity.
Hepcidin
•Binds ferroportin, complex internalised and
degraded.
•Resultant decrease in efflux of iron from
cells to plasma
Hepcidin
•Iron – stimulated with increased iron levels
•Inflammation, infection (and endotoxin)
•Hypoxia - downregulated
•Erythropoiesis – downregulated in anaemia,
oxidative stress, ineffective erythropoiesis.
Regulation of hepcidin
•BMP - members of TGF-b superfamily which
regulate cell proliferation, differentiation,
apoptosis.
•Targets BMP receptors type I and II, resulting in
phosphorylation of cytoplasmic R-Smads.
•R-Smads associate with Smad4, translocate to
nucleus, activates transcription of target genes (in
this case hepcidin).
Hepcidin regulation by bone
morphogenic protein pathway
•Production stimulated by increased plasma
iron and tissue stores.
•Negative feedback - hepcidin decreases
release of iron into plasma (from
macrophages and enterocytes).
•Fe-Tf increases hepcidin mRNA production
(dose dependent relationship).
Hepcidin regulation by iron
TREATMENT
Iron :
Iron is normally taken in the form of ferrous sulfate.
Although other iron salts are commercially available and
make claims of fewer or less severe side effects, these
benefits may be related to the fact that other preparations
contain less iron by weight. Ferrous sulfate contains
about 37% iron, while ferrous gluconate contains only
about 13% iron. People who have trouble with the side
effects of ferrous sulfate may benefit from some of the
specialty preparations available, but ferrous sulfate
normally offers the greatest amount of iron of all
commercial products.
Recommended dosage :
Dosage should be calculated by iron needs,
based on laboratory tests.
Recommended one tablet a day,
containing 65 mg of iron, as a supplement for
patients over the age of 12 years.
Precautions
Iron can lead to lethal poisoning in children. All iron supplements
should be kept carefully out of reach of children.
Some types of anemia do not respond to iron therapy, and the use
of iron should be avoided in these cases.
People with acquired hemolytic anemia, autoimmune hemolytic
anemia, hemochromatosis, hemolytic anemia and hemosiderosis
should not take iron supplements.
Iron supplements should also be avoided by people who have
gastric or intestinal ulcers, ulcerative colitis, or Crohn's disease.
These conditions marked by inflammation of the digestive tract,
which would be made worse by use of iron.
Side effects :
The most common side effects of iron
consumption are stomach and intestinal
problems, including stomach upset with
cramps, constipation, diarrhea, nausea, and
vomiting.
At least 25% of patients have one or more of
these side effects. The frequency and severity of
the side effects increases with the dose of iron.
Less frequent side effects include heartburn and
urine discoloration.
Interactions
Iron supplements should not be taken at the same time
as antibiotics of either the tetracycline or quinolone types.
The iron will reduce the effectiveness of the antibiotic.
Also, iron supplements reduces the effectiveness of
levodopa, which is used in treatment of Parkinson's
disease.
Iron supplements should not be used with magnesium
trisilicate, an antacid, or with penicillamine, which is used
for some types of arthritis.
Taking iron with vitamin C increases the absorption of iron,
with no increase in side effects.
Folic acid :
Folic acid is found in many common foods, including
liver, dried peas, lentils, oranges, whole-wheat products,
asparagus, beets, broccoli, brussel sprouts, and spinach.
However, in some cases, patients have difficulty
absorbing folic acid or in converting it from the form
found in foods to the form that is active in blood
formation.
In these cases, folic acid tablets are appropriate for use.
Recommended Dose :
For treatment of anemia, a daily dose of 5 mg is generally used.
Patients who have trouble absorbing folic acid may require
higher doses.
Maintenance doses are:
infants: 0.1 mg/day
children (under 4 years of age): up to 0.3 mg/day
children (over 4 years of age) and adults: 0.4 mg/day
pregnant and lactating women: 0.8 mg/day
Precautions:
Before treating an anemia with folic acid, diagnostic
tests must be performed to verify the cause of the
anemia.
Pernicious anemia caused by lack of vitamin
B
12
shows symptoms that are very similar to those of
folic acid deficiency but also causes nerve damage
which shows up as a tingling sensation and feelings of
numbness.
Giving folic acid to patients with B
12
deficiency anemia
improves the blood cell count, but the nerve damage
continues to progress.
SIDE EFFECTS.
Folic acid is considered extremely safe, and there are no
predictable side effects.
Where side effects have been reported, they have been
among patients taking many times more than the normal
therapeutic dose of the drug.
On rare occasions allergic reactions to folic acid have
been reported.
INTERACTIONS.
Phenytoins, used to treat seizure disorders, interact with folic
acid with a reduction in phenytoin effectiveness and an increased
risk of seizures.
If the two drugs must be used together, phenytoin blood levels
should be monitored, and the dose may have to be increased.
Trimethoprim (an antibacterial) and Methotrexate (originally an
anti-cancer drug, which is also used for arthritis and psoriasis) act
by reducing the metabolism of folic acid.
Regular blood monitoring is required, and dose adjustments may
be needed.
Vitamin B
12
is also known as
cyanocobalamine and hydroxocobalamine.
Cyanocobalamine may be given by mouth, while hydroxocobalamine
must be injected.
The vitamin has many functions in the body, including maintaining the
nervous system, but in treatment of anemia B
12 is needed for the
metabolism of folic acid. Lack of B
12
causes pernicious anemia, a type
of anemia which is marked by a low red cell count and lack of
hemoglobin.
There are many other symptoms of pernicious anemia, including a
feeling of tingling or numbness,shortness of breath, muscle weakness,
faintness, and a smooth tongue. If pernicious anemia is left untreated
for more than three months, permanent damage to the nerves of the
spinal cord may result.
Recommended Dose :
While vitamin B
12
can be given by mouth for mild vitamin
deficiency states, pernicious anemia should always be treated with
injections, either under the skin (subcutaneous) or into muscle
(intramuscular). Hydroxocobalamine should only be injected into
muscle. Intravenous injections are not used because the vitamin
is eliminated from the body too quickly when given this way.
Elderly patients, whose ability to absorb vitamin B
12 through the
stomach may be impaired, should also be treated with injections
only.
The normal dose of cyanocobalamine is 100 mcg (micrograms)
daily for six to seven days. If improvement is seen, the dose may
be reduced to 100 mcg every other day for seven doses and then
100 mcg every three to four days for two to three weeks. After
that, monthly injections may be required for life.
PRECAUTIONS.
Although vitamin B
12
has a very high level of safety,
commercial preparations may contain preservatives
which may cause allergic responses.
In patients with pernicious anemia, treatment with
vitamin
B
12
may lead to loss of potassium. Patients should be
monitored for their potassium levels.
SIDE EFFECTS.
Diarrhea and itching of the skin have been
reported on rare occasions.
Moreover, there have been reports of severe
allergic reactions to cyanocobalamine.
INTERACTIONS.
Aminosalicylic acid may reduce the effectiveness of vitamin
B
12
.
Also, Colchicine, a drug used for gout, may reduce the
effectiveness of vitamin B
12
.
Other, infrequently used drugs and excessive use of alcohol may
also affect the efficacy of vitamin B
12
.
Anabolic steroids :
The anabolic steroids (nandrolone, oxymetholone,
oxandrolone, and stanzolol) are the same drugs that are used
improperly by body builders to increase muscle mass.
Two of these drugs, nandrolone and oxymetholone, are
approved for use in treatment of anemia.
Nandrolone is indicated for treatment of anemia caused by
kidney failure, while Oxymetholone may be used to treat
anemia caused by insufficient red cell production, such
as aplastic anemia.
All anabolic steroids are considered to be drugs of abuse under
F.D.A and only recommended under certain circumstances.
RECOMMENDED DOSAGE.
The information that follows is specific only to oxymetholone;
however, the warnings and precautions apply to all drugs in the
class of anabolic steroids.
The dosage of oxymetholone must be individualized.
The most common dose is 1 to 2 mg per kilogram of body
weight per day, although doses as high as 5 mg per kilogram per
day have been used.
The response to these drugs is slow, and it may take several
months to see if there is any benefit.
PRECAUTIONS.
All anabolic steroids are dangerous. The following warnings
represent the most significant hazards of these drugs.
Peliosis hepatitis, a condition in which liver and sometimes
spleen tissue is replaced with blood-filled cysts, has occurred in
patients receiving androgenic anabolic steroids.
Although this condition is usually reversible by discontinuing the
drug, if it is left undetected and untreated, it may lead to life-
threatening liver failure or bleeding.
Liver tumors may develop. Although most of these tumors are
benign and will go away when the drug is discontinued, liver
cancers may also result.
Anabolic steroids may cause changes in blood lipids, leading
to atherosclerosis with greatly increased risk of heart attack.
Because anabolic steroids are derived from male sex hormones,
masculinization may occur when they are used by women.
Elderly men who use these drugs may be at increased risk of
prostate enlargement and prostate cancer.
Increased water retention due to anabolic steroids may lead to
heart failure.
Anabolic steroids should not be used during pregnancy, since this
may cause masculinization of the fetus.
Anabolic steroids should be used in children only if there is no
possible alternative. These drugs may cause the long bones of the
legs to stop growing prematurely, leading to reduction in adult
height. Regular monitoring is essential.
In patients with epilepsy, the frequency of seizures may be
increased.
In patients with diabetes, glucose tolerance may be altered.
Careful monitoring is essential.
SIDE EFFECTS.
The list of side effects associated with anabolic steroids is
extremely long. The following list covers only the most commonly
observed effects:
acne
increased urinary frequency
breast growth in males
breast pain
persistent, painful erections
masculinization in women
INTERACTIONS :
Anabolic steroids should not be used in combination with
anticoagulants such as warfarin.
Anabolic steroids increase the effects of the anticoagulant,
possibly leading to bleeding.
If the combination cannot be avoided, careful monitoring
is essential.
Erytropoetin :
Erythropoietin is a glycoprotein hormone that controls erythropoiesis,
or red blood cell production. It is a cytokine for erythrocyte (red blood
cell) precursors in the bone marrow and has its primary effect on red
blood cells by promoting red blood cell survival through protecting
these cells from apoptosis. It also cooperates with various growth
factors involved in the development of precursor red cells. And A
similar drug, darepoetin alpha, is available with the same properties,
but it remains active longer and so requires fewer injections each week.
Epoetin alpha is approved by the Food and Drug Administration for
the following uses:
anemia associated with chronic renal failure
anemia related to zidovudine therapy in HIV-infected patients
anemia in cancer patients on chemotherapy
reduction in blood transfusions in surgical patients
RECOMMENDED DOSAGE.:
Dosing schedules may vary with the cause of the anemia.
All doses should be individualized.
In general, epoetin alpha dosing in adults is started at 50 to 100
units per kilogram given three times a week, either by vein or
subcutaneously.
PRECAUTIONS.
Epoetin alpha should not be given to patients with severe,
uncontrolled hypertension.
Other conditions in which epoetin alpha should be used only when
the benefits clearly outweigh the risks are as follows:
constitutional aplastic anemia
hypertension
thromboembolism
Side effects :
The most common adverse effects of erythopoetin alpha are:
joint pain
chest pain
diarrhea
swelling
fatigue
fever
weakness
headache
high blood pressure
irritation at injection site
nausea
vomiting
rapid heart beat