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7. haematology > Microcytic Anaemia > Flashcards

Microcytic Anaemia Flashcards

1
Q

Briefly outline how iron is absorbed/transported/stored.

A

Absorbed in duodenum/jejunum

Transported by transferrin

Stored in ferritin + haemosiderin

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2
Q

Define anaemia.

A

Present when there is a decrease of haemoglobin in the blood below the reference level for the age and sex of the individual.

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3
Q

Give 3 signs of anaemia.

A
  1. Pale skin and mucous membranes.
  2. Tachycardia.
  3. Bounding pulse.
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4
Q

What are the 4 measurements that anaemia is defined by?

A
  1. RBCs
  2. Hb
  3. Haematocrit
  4. MCV (mean corpuscular volume -> the average volume of RBC’s, I.E. basically their size)
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5
Q

Normal range for mean corpuscular volume (MCV)?

A

80-100fL
< than this = microcytic
> = macrocytic

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6
Q

Define microcytic anaemia.

A

Low MCV
Small RBCs
MCV <80Fl
Problems in producing RBCs or Hb

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7
Q

What are the 5 main causes of microcytic anaemia?

A

TAILS:
T - Thalassemia
A - Anaemia of chronic disease
I - Iron deficiency anaemia
L - Lead poisoning
S - Sideroblastic anaemia

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8
Q

What is the most common anaemia worldwide?

A

Iron-deficiency anaemia

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9
Q

Give 4 categories of iron storage being used up in iron-deficiency anaemia and an example of each.

A
  1. Poor diet / Dietary insufficiency
    - Especially in children and babies (but rarely in adults) where there is poverty
  2. Blood loss / bleeding
    - Menorrhagia (severe menstruation with heavy blood loss)
    - GI ulcers + bleeding -> H.pylori -> bacteria uses iron
    - Colon cancer
    - Hookworm - the leading cause of iron deficiency worldwide, resulting in GI blood loss
  3. Malabsorption of iron
    - Crohn’s disease
    - Coeliac disease
    - PPIs -> reduce stomach acid -> stomach acid keeps iron in Fe2+ soluble form, reduced acid allows conversion to insoluble Fe3+
  4. Increased requirements
    - Pregnancy
    - Growth
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10
Q

Possible presenting features of iron-deficiency anaemia?

A

Koilonychias (spoon nails).
Mouth changes - angular stomatitis, atrophic glossitis.
Fatigue, pallor - conjunctival, faintness, dyspnoea.
Pica (classic = ice craving).

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11
Q

What investigations/diagnostic tests might you do in someone with anaemia?

A
  1. Blood tests: FBC (full blood count) and blood film.
    (Hb, haematocrit, MCV, MCHC, peripheral blood smear)
  2. Iron studies
    (Serum ferritin, Serum iron, Serum soluble transferrin receptors)
  3. B12 levels
  4. Reticulocyte count

Tests for underlying cause e.g. coeliac serology, endoscopy, biopsy,

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12
Q

Describe what is seen on a peripheral blood film in iron-deficiency anaemia.

A

Microcytic hypochromic RBCs, varying in size and shape (anisocytosis and poikilocytosis)

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13
Q

In iron-deficiency anaemia, what will happen to the iron, ferritin and total iron binding capacity (TIBC) (AKA iron studies)?

A

Iron and ferritin are decreased.
TIBC is increased.
Transferrin saturation = low.

NB - ferritin is acute phase protein, so may be raised in inflammation/infection/malignancy

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14
Q

How would you treat iron-deficiency anaemia?

How long would this treatment be given?

A

Oral iron - ferrous sulphate - given until anaemia resolved + further 3-6/12

Consider transfusion, if symptomatic at rest w/ dyspnoea and chest pain.

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15
Q

What are some SEs of ferrous sulphate?

A

Nausea, abdominal discomfort, diarrhoea/constipation, black stools

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16
Q

What is thalassaemia?

A

A haemoglobin disorder of quantity. There is reduced synthesis of one or more globin chains with leading to a reduction in Hb -> anaemia.

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17
Q

Define alpha thalassaemia.

A

Autosomal recessive haemoglobinopathy which causes microcytic anaemia.

A genetic defect in the protein chains that make up Hb.

Normal Hb consists of 2x α and 2x β-globin chains.

Defects in α-globin chains leads to alpha thalassaemia.

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18
Q

Which heritage is a risk factor for alpha thalassaemia?

A

Asian and African heritage

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19
Q

Which chromosome is responsible for alpha thalassaemia?

A

Chromosome 16 :
- 4 alleles on chromosome 16 for alpha-chain synthesis

20
Q

How many alpha globin gene deletions may a patient have and still appear clinically normal?

A

1 - and would be silent carrier.

21
Q

What are the serious risks of alpha thalassaemia major?

A

Leads to high-output HF; hepatosplenomegaly and oedema (hydrops fetalis)

22
Q

Describe the features of a 2 gene deletion alpha thalassaemia.

A

Alpha thalassaemia trait.

Microcytosis ± mild anaemia - mixed up with IDA a lot.

23
Q

Describe the features of a 3 gene deletion alpha thalassaemia.

A

Leads to beta tetramers, which are detected on electrophoresis.
aka HbH disease.

Cannot form α + β chains for tetramers (HbH), causing RBC damage and disease → high O2 affinity and won’t release to tissues

Moderate anaemia symptoms and splenomegaly, jaundice / gallstones.

May present in childhood (more severe), with family history, from the right geographical areas.

24
Q

Describe the features of a 4+ gene deletion alpha thalassaemia

A

AKA major alpha thalassaemia (Hb Barts) or Bart Hydrops Fetalis.

No alpha chains synthesised.

Death in utero (because gamma chainsform tetramers that cannot carry O2 efficiently).

25
Q

What would you see on investigation for alpha thalassaemia?

A
  1. FBC
    - Microcytic (low MCV and MCHC)
    - Elevated reticulocyte %
  2. Peripheral blood smear / blood film
    - Microcytic/hypochromic, target cells
    - Basophilic stippling in 3 gene/HbH
  3. Haemoglobin analysis
    - Detects HbH or Hb Bart but won’t detect silent carrier or trait.
  4. Iron studies
    - Serum iron/ferritin both normal or elevated
26
Q

Describe the treatment of alpha thalassaemia.

A

1) Silent carrier = genetic counselling + education and iron advice (avoid unless deficient)

2) Trait = genetic counselling + education and iron advice

3) HbH = genetic counselling + folic acid (1mg, PO) + education. Also: regular transfusion to >10g/dL + iron monitoring with chelation ± splenectomy ± assess for haematopoeitic stem cell transplant

4) Crisis = Identify cause + monitor + folic acid ± red cell transfusion

27
Q

If someone has beta thalassaemia, do they have more alpha or beta globin chains?

A

They have very few beta chains, alpha chains are in excess.

28
Q

How does beta thalassaemia cause anaemia?

A

Decreased/absent synthesis of beta-globin leads to excess alpha production + membrane damage/cell destruction.

Get ineffective erythropoeisis and increased haemolysis.

29
Q

What is the clinical classification of beta thalassaemia?

A
  1. Thalassaemia major.
  2. Thalassaemia intermedia.
  3. Thalassaemia carrier/heterozygote.
30
Q

Which clinical classification of thalassaemia is often asymptomatic?

A

Thalassaemia carrier/heterozygote.

31
Q

Which clinical classification of thalassaemia relies on regular transfusions?

A

Thalassaemia major.

32
Q

What are the features of minor beta thalassaemia?

A

Dymptomless carrier state. mild anaemia. hypochromic and microcytic. often gets muddled with IDA.

Beta/beta+ or beta/beta0

(Silent carrier has normal haem parameters)

33
Q

What are the features of medium (aka intermediate) beta thalassaemia?

A

Presents similarly to major but as a toddler rather than in first year.

Beta+/beta+ or beta0/beta+
Doesn’t require transfusions.

34
Q

What are the features of major beta thalassaemia?

A

Severe anaemia - needs regular transfusions.

Presents in 1st year with progressive pallor, abdominal distension (hepatosplenomegaly) and characteristic head shape (skull bossing), failure to thrive.

Beta0/beta0

35
Q

What would you see on investigation for beta thalassaemia?

A
  • FBC = microcytic anaemia
  • Peripheral blood smear = microcytic, target cells, nucleated red cells.
  • Reticulocyte count = elevated (haemolytic)
  • Hb analysis (electrophoresis):
    major = no HbA, elevated HbF and HbA2
    medium = decreased HbA, elevated HbF and HbA2
    minor = mostly HbA, elevated HbF and HbA2.
  • LFT = elevated total and unconjugated bilirubin (haemolytic)
  • XR skull = “hair on end” sign, widening of diploeic space
  • abdo USS = hepatosplenomegaly
36
Q

How would you treat beta thalassaemia?

A

1) Minor/trait = genetic counselling, iron advice (avoid unless deficient)

2) Medium = genetic counselling, transfusion if symptomatic anaemia (e.g. infection, periop) + iron monitoring with chelation (desferrioxamine)

3) Major = genetic counselling + regular transfusion to >10g/dL + iron monitoring with chelation.
± splenectomy
± assess for haematopoeitic stem cell transplant (curative)

37
Q

Why is it important to monitor iron levels in someone with beta thalassaemia major?

A

There is a risk of iron overload from the regular transfusions.

Excess iron will be deposited in various organs e.g. the liver and spleen and cause fibrosis

38
Q

When do people with beta thalassaemia major usually present and why?

A

These patients usually present very young due to having severe anaemia and so a failure to feed/thrive.

39
Q

What might you see on a blood count taken from someone with beta thalassaemia major?

A
  1. Raised reticulocyte count.
  2. Microcytic anaemia.
40
Q

Give some possible complications of beta thalassaemia

A

Thrombotic.

Those due to iron overload: arthropathy, pigmentation/bronzing, arrhythmias (leading to CCF), endocrine (ant. pituitary and pancreatic islet cells - slowed growth, delayed puberty, T1DM).

Yransfusion reactions + transmission acquired infections (HIV, HBV, HCV).

Splenectomy complications.

41
Q

Give an example of an iron chelator.
How do these drugs work?

A

Desferrioxamine.
Binds free iron in bloodstream and enhance its elimination in urine.

42
Q

What is a sideroblast?

A

An atypical, abnormally nucleated erythroblast with perinuclear iron accumulation

43
Q

What is sideroblastic anaemia?

A

Think of it as microcytic hypochromic anaemia that doesn’t respond to iron.

Inherited or acquired disorder - body has enough iron but can’t incorporate it into Hb (ineffective erythopoeisis).

Iron absorption is increased.

44
Q

Give 3 causes of sideroblastic anaemia.

A
  • Inherited (XLSA - X-linked)
    -Mmyelodysplastic syndrome (MDS)
  • Myeloma
  • PRV
  • Pyridoxine (B6) deficiency
  • Drugs (isoniazid)
  • Alcohol misuse
  • Lead toxicity.
45
Q

Investigations for sideroblastic anaemia?

A

Microcytic hypochromic anaemia.

Blood film = dimorphic population of normal and hypochromic red blood cells.

Iron studies: serum iron high, serum ferritin high, TIBC low.

BM aspirate = presence of sideroblasts:
- “perinuclear ring of iron granules with Prussian Blue staining”

46
Q

How would you treat sideroblastic anaemia?

A

Mostly supportive.
Iron chelation - desferrioxamine.

Repeated RBC transfusions if needed.
Avoid alcohol + Vit. C (they increase iron absorption).

If hereditary - consider Pyridoxine (vit B6).

7. haematology (15 decks)

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