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Metabolism, Endocrinology and Haematology > Session 4- Introduction to anaemia & Vitamin B12 and folate metabolism > Flashcards

Session 4- Introduction to anaemia & Vitamin B12 and folate metabolism Flashcards

1
Q

define anaemia

A

a haemoglobin concentration lower than the normal range which varies

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2
Q

clinical signs of anaemia

A

glossitis, spoon shaped nails, angular chelitis

-Pallor
• Tachycardia
• Systolic flow murmur
• Tachypnoea
• Hypotension
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3
Q

symtoms of anaemia

A 
Shortness of breath
• Palpitations
• Headaches
• Claudication
• Angina
• Weakness & Lethargy
• Confusion
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4
Q

key clinical point of anaemia

A

Anaemia in itself is not a diagnosis but a
manifestation of an underlying disease state and it
is important to establish the cause of the anaemia

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5
Q

specific signs associated with the cause of anaemia

A

Koilonychia

Glossitis

Angular stomatitis

Abnormal facial bone
development
Rare in recent times as
preventable with early diagnosis

Thalassaemia

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6
Q

koilonychia

A

(Spoon shaped nails)

Iron deficiency

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7
Q

glossitis

A

(inflammation & depapillation of tongue)

Vitamin B12 deficiency

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8
Q

angular stomatitis

A

(Inflammation of corners of the mouth)

Iron deficiency

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9
Q

why might anaemia develoop- bone marrow

A 
Reduced or dysfunctional
erythropoiesis
Abnormal Haem synthesis
Abnormal globin chain
synthesis
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10
Q

why might anaemia develop- peripheral red blood cells

A

abnormal structure
mechanical damage
abnormal metabolism

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11
Q

removal- spleen

why might anaemia develop

A

increased removal by reticuloendothelial system

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12
Q

what is the role of erythropeitin in the hormonal control of erythropoiesis

A

when there is low blood oxygen pericytes in kidney sense hypoxia and produce erythropoietin

EPO travels in bloodstream and binds to receptors on erythblasts in bone marrow and stimulates red cell production

increased number of red cells in blood

high blood oxygen

negative feedback on pericytes

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13
Q

why might anaemia develop in reduced or dysfuntional erythpoiesis

A

Anaemia can result from marrow being
unable to respond to EPO

myelofibrosis

anaemia of chronic disease

myelodysplastic syndroms

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14
Q

myelofibrosis

A

If marrow is infiltrated by cancer cells
or fibrous tissue (myelofibrosis) the
number of normal haemopoietic cells is
reduced

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15
Q

anaemia of chronic disease

A

In Anaemia of chronic disease e.g. in
rheumatoid arthritis, iron is not made
available to marrow for rbc production

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16
Q

myelodysplastic syndrome

A 
In rare forms of blood cancer called
myelodysplastic syndromes
abnormal clones of marrow stem cells
limit the capacity to make both red and
white blood cells
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17
Q

why might anaemia develop- defects in haemoglobin synthesis

A

Defects in the haem synthetic
pathway can lead to
Sideroblastic anaemia

Insufficient iron in diet can lead
to iron deficiency anaemia (not
enough iron to make Haem)
Anaemia of chronic disease can
result in a functional iron
deficiency (sufficient iron in body
but not made available for
erythropoiesis

mutations in the genes encoding the globin chain proteins
• α Thalassaemia
• β Thalassaemia
• Sickle cell disease

18
Q

why might anaemia develop- defects in red cell metabolism

A

G6DPH deficiency

pyruvate kinase deficiency

19
Q

why might anaemia devlop- excessive bleeding

A

Chronic bleeding

• Heavy menstrual bleeding
• Repeated nosebleeds
• Haemorrhoids
Occult gastrointestinal bleeding
(blood lost in stool)
   • Ulcers (stomach or
small intestine)
    • Diverticulosis
    • Polyps in large intestine
    • Intestinal cancer
• Kidney or bladder tumours (blood
lost in urine)
20
Q

autoimmune haemolytic anaemia

A

autoantibodies bind to the red cell membrane
proteins causing them to be recognised by
macrophages in the spleen and destroyed

21
Q

2 key features can help to work out the cause of an anaemia

A
  • The rbc size – macrocytic, microcytic, normocytic (big, small, normal)
  • The presence or absence of reticulocytosis (has the marrow responded normally?)
22
Q

reticulocytes

A

• Immature red blood cells (i.e. those which have just
been released from the marrow into blood)
• No nucleus & eliminate remaining mitochondria
• Typically compose ~1% of all red blood cells and take
~ 1 day to mature into erythrocytes

23
Q

macrocytic anaemia

FAT RBC

A

foetus- increased folate demand in late pregnancy

alcohol- toxicity towards bone marrow + secondary likely B12/Folate deficiency

hypoThyrodism- low thyroid hormones affect hormones involved in haemopoiesis

reticulocytes- secondary to blood loss, many reticulocytes are produced

B12/Folate- deficiency/pernicious- thymine deficiency- uracil used - constant DNA repaire - nucleus never matures, glossitis

Cirrhosis/ chronic liver disease- not fully confirmed yet, maybe excess cholesterol deposition

24
Q

megaloblastoc anaemia

A 
• Interference with DNA
synthesis during erythropoiesis
causes development of nucleus
to be retarded in relation to
maturation of cytoplasm
• Cell division delayed and
erythroblasts continue to grow
to form megaloblasts which
give rise to larger red cells
25
Q

macronormoblastic erythropoiesis

A 
• Normal relationship between
development of nucleus and
cytoplasm is retained but
erythroblasts are larger than
normal and give rise to larger
red cells
26
Q

stress erythropoiesis

A 
Conditions associated with a
high reticulocyte count
(reticulocytes are larger than
normal red cells)
• High level of erythropoietin
leads to an expanded and
accelerated erythropoiesis
27
Q

microcytic anaemia

TAILS

A

These anaemias present with a reduced RBC size that are often pale (hypochromic)

Thalassaemia: Reduced/absent synthesis of a globin chain in haemoglobin → abnormal facial bone
development as the bone marrow tries to ramp up haemopoiesis

Anaemia of chronic disease: Reduced iron availability (covered in a few slides)

Iron deficiency: insufficient iron available to meet haem synthesis requirements

Lead poisoning: inhibits haem synthesis enzymes

Sideroblastic anaemia: genetic defect in haem synthesis

28
Q

normocytic anaemia

A

These anaemias present with normal sized RBCs

Acute blood loss: blood volume has been lost, but no effect on RBC structure/size

Bone marrow failure (aplastic): either inherited or acquired, the bone marrow stem cells can no
longer produce sufficient RBCs to meet the demands of the body.

Chronic disease: Reduced iron availability

Destruction (haemolytic): abnormal excess breakdown of RBCs

29
Q

what causes folate deficiency

A 
• Dietary deficiency (Poor diet)
• Increased requirements
• Pregnancy
• Increased erythropoiesis e.g.
haemolytic anaemia
• Severe skin disease (e.g.
psoriasis, exfoliative dermatitis)
• Disease of the duodenum and
jejunum (e.g. coeliac disease,
Crohn’s disease)
• Drugs which inhibit dihydrofolate
reductase (e.g. Methotrexate)
• Alcoholism (poor diet and damage
to intestinal cells)
• Urinary loss of folate in liver
disease and heart failure
30
Q

symtoms of folate deficiency

A 
Those related to anaemia
• Reduced sense of taste
• Diarrhoea
• Numbness and tingling in feet and
hands
• Muscle weakness
• Depression
31
Q

vitamin B12 absorption

A 
• B12 released from food proteins by
proteolysis in stomach where it then
binds to haptocorrin
• Haptocorrin B12 complex digested by
pancreatic proteases in small
intestine releasing B12 which then
binds intrinsic factor (produced by
gastric parietal cells).
• Intrinsic factor–B12 complex binds to
cubam receptor which mediates
uptake of complex by receptormediated endocytosis into
enterocytes
• After lysosomal release in
enterocytes, B12 exits via basolateral
membrane through MDR1
• Binds to transcobalamin in blood
and transported around bloodstream
32
Q

causes of B12 deficiency

A 
-Dietary deficiency (Vegan diet lacking
B12 supplementation)
• Lack of intrinsic factor (Pernicious
anaemia)
• Diseases of the ileum (Crohn’s disease,
ileal resection, tropical sprue)
• Lack of transcobalamin (congenital
defect)
• Chemical inactivation of B12 e.g.
frequent use of anaesthetic gas nitrous
oxide
• Parasitic infestation (rare tapeworm
found in fish can trap B12)
• Some drugs can chelate intrinsic factor
(e.g. hypercholesterolaemia drug
Cholestyramine)
33
Q

symptoms of b12 deficiency

A 
Those related to anaemia
• Glossitis & mouth ulcers
• Diarrhoea
• Paraesthesia
• Disturbed vision
• Irritability
34
Q

symotoms of subacute combined degeneration of the cord

A

degeneration of posterior and lateral columns of the spinal cord

• Gradual onset weakness,
numbness & tingling in arms,
legs & trunk which progressively
worsens.
• Changes in mental state
35
Q

how can folate/ b12 defiency affect the nervous system

A 
• Folate deficiency in
pregnancy can cause neural
tube defects
• Vitamin B12 deficiency
associated with focal
demyelination
36
Q

why do b12 and folate deficiency cause a megaloblastic anaemia

A

• Vitamin B12 and folate are both necessary for
nuclear division and maturation.
• When B12 and folate are deficient, nuclear
maturation and cell divisions lag behind
cytoplasm development.
• Leads to large red cell precursors with
inappropriately large nuclei and open
chromatin. The mature red cells are also
large leading to a macrocytic anaemia

37
Q

anisopikilocytosis

A

variance in size and shape

38
Q

treatment of vitamin b12 deficiency

A

For Pernicious anaemia: Hydroxycobalamine intramuscular (NOT oral) for life

For other causes of B12 deficiency: oral cyanocobalamine

39
Q

what is Hb1AC

A

glycated haemoglobin which is when Hb is linked to a sugar

40
Q

what is haemoglobinaemia

A

excess haemoglobin in the blood. If the normal reticuloendothelial pathway for removal of red blood cells is overwhelmed or haemolysis is very severe (e.g. due to incompatible blood transfusion), a direct breakdown of red blood cells rusults in release of haemoglobin into the circulation

41
Q

coombs test

A

autoantibody test for autoimmune haemoltyic anaemia

42
Q

what is pernicious anaemia

A

autoantibodies interfering with the production or function of intrinsic factor

Intrinsic factor is essential for the absorption of vitamin B12 in the ileum. Without intrinsic factor, vitamin B12 deficiency will occur and production of red blood cells will be impaired causing anaemia. “Pernicious” means “deadly”. Pernicious anemia was often fatal in the past before vitamin B12 treatments were available.

Metabolism, Endocrinology and Haematology (20 decks)

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