2. Megaloblastic anemia is a form of anemia
characterized by very large sized red blood cells
and a decrease in the number of those cells.
It occurs mainly due to deficiency of vitamin B12
and folic acid.
Pernicious anemia is a type of megaloblastic
anemia in which the body isn't able to absorb
vitamin B12 due to a lack of intrinsic factor in
stomach secretions.
Intrinsic factor is needed for the body to absorb
vitamin B12.
3. 1)Vitamin B12 deficiency
Vitamin B12 deficiency occurs due to
i. Achlorhydria-induced malabsorption (prevents small
intestine to absorrb nutrient from food)
ii. Deficient intake
iii. Deficient intrinsic factor, a molecule produced by cells in
the stomach that is required for B12 absorption
(pernicious anemia or gastrectomy)
iv. Coeliac disease (immune system attacks own tissue)
v. Biological competition for vitamin B12 by diverticulosis,
fistula, intestinal anastomosis, or infection by the marine
parasite Diphyllobothrium latum (fish tapeworm)
vi. Selective vitamin B12 malabsorption (congenital—juvenile
megaloblastic anemia 1—and drug-induced)
4. 2) Folate deficiency Folic acid deficiency occurs
due to:
i. Alcoholism
ii. Deficient intake
iii. Increased needs in following conditions-
Pregnancy,Infant,Rapid cellular proliferation,
Cirrhosis.
iv. Malabsorption (congenital or drug-induced) v.
Intestinal and jejunal resection vi. Deficiency of
thiamine and factors (e.g. enzymes)
responsible for folate metabolism
5. 3) Combined Deficiency of vitamin B12 and folic
acid
4) Toxins and Drugs Megaloblastic anemia may
also be develop due to administration of
antimetabolites that affects DNA production
directly, such as some chemotherapeutic or
antimicrobial agents (for like azathioprine or
trimethoprim). • Folic acid antagonists
(methotrexate). • Purine synthesis antagonists
(6-mercaptopurine, azathioprine). • Pyrimidine
antagonists (cytarabine).
6. Megaloblastic anemia results from
inhibition of DNA synthesis during red blood cell
production. When DNA synthesis is impaired, the
cell cycle cannot progress from the G2 growth stage
to the mitosis (M) stage. This leads to continuing
cell growth without division, which presents as
macrocytosis. Megaloblastic anemia has a rather
slow onset, especially when compared to that of
other anemias.
7. The defect in red cell DNA
synthesis is most often due to decrease supply
of vitamins, specifically vitamin B12 and folic
acid. In the bone marrow, most megaloblasts are
destroyed prior to entering the peripheral blood
(intramedullary hemolysis) some can escape the
bone marrow (macrocytes) to peripheral blood
but they are destroyed by the reticulo-
endothelial system (extramedullay hemolysis).
This reduces the number of red blood cells.
8. i. Shortness of breath
ii. Muscle weakness
iii. Abnormal paleness of the skin
iv. Glossitis (swollen tongue)
v. Loss of appetite/weight loss
vi. Diarrhea vii. Nausea
vii. Fast heartbeat
viii. Smooth or tender tongue
ix. Tingling in hands and feet
9. 1) Complications of vitamin B12 deficiency A lack
of vitamin B12 can cause the following
complications: i) Neurological changes A lack of
vitamin B12 can cause neurological problems,
such as: •Vision problems. • Memory loss. • Pins
and needles (paraesthesia). • Loss of physical
coordination (ataxia), which can affect whole
body and cause difficulty speaking or walking. •
Damage to parts of the nervous system
(peripheral neuropathy), particularly in the legs.
• If neurological problems do develop, they may
be irreversible
10. ii) InfertilityVitamin B12 deficiency can sometimes lead to
temporary infertility (an inability to conceive).This usually
improves with appropriate vitamin B12 treatment.
ii) Stomach cancer Pernicious anemia (vitamin B12 deficiency)
increases the risk of stomach cancer.
iv) Neural tube defects For pregnant women not having
enough vitamin B12 can increase the risk of developing a
serious birth defect known as a neural tube defect.The
neural tube is a narrow channel that eventually forms the
brain and spinal cord. Examples of neural tube defects
include:
• Spina bifida — where the baby's spine doesn't develop
properly.
• Anencephaly — where a baby is born without parts of the
brain and skull.
• Encephalocele — where a membrane or skin-covered sac
containing part of the brain pushes out of a hole in the skull.
11. 2) Complications of folate deficiency
A lack of folic acid can also cause complications, such as:
i) Infertility- As with a lack of vitamin B12, a folate
deficiency can also affect fertility. However, this is
only temporary and can usually be reversed with
folic acid supplements.
ii) Cardiovascular disease
iii) Cancer- Research has shown that folate deficiency
can increase risk of some cancers, such as colon
cancer.
iv) Problems in childbirth- A lack of folate during
pregnancy may increase the risk of the baby being
born prematurely (before the 37th week of
pregnancy) or having a low birthweight.
v) Neural tube defects (Defect of brain, spine & spinal
cord)
12. Complete blood count (CBC)
Test for Folate Deficiency
Bone marrowTest
15. The anemia which involves the genetic or hereditary factors
is as follows:
1) Sickle-cell anemia
2)Thalassemia
3) Congenital pernicious anemia-This is characterized by an
inability to produce intrinsic factor which causes absorption
of vitamin B12.Without vitamin B12, the body cannot make
enough healthy red blood cells, causing anemia.
4) Fanconi anemia-This is characterized by the decreased
functioning of bone marrow.The bone marrow fails to
produce sufficient quantity of blood cells for the body.
Besides having the classic signs of anemia, such as fatigue
and dizziness, some people with Fanconi anemia are also at
greater risk for infection because their bodies don't produce
enough white blood cells to fight germs. Some patients are
also at greater risk for acute myeloid leukemia, a type of
blood cancer, because their bone marrow makes a large
number of immature white blood cells, preventing the
production of normal blood cells.
16. 5) Hereditary spherocytosis-This disease is
characterized by formation of abnormal red blood
cells called spherocytes that are thin and fragile.These
cells cannot change shape to pass through certain
organs as normal red blood cells do, so they stay in the
spleen longer, where they are eventually destroyed.
The destruction of the red blood cells causes anemia.
6)Thrombotic thrombocytopenic purpura(TTP)-This
occurs due to condition results from a certain faulty
blood-clotting enzyme, leading to the clumping of
platelets, which are blood cells that help heal wounds.
When platelets clump together, fewer platelets are
circulating throughout the body, so people withTTP
can experience prolonged bleeding internally,
externally, or under the skin. It can result in anemia by
affecting red blood cells once they get out of the bone
marrow, causing breakages of those red blood cells in
the blood.
