L5: Causes of Anaemia Flashcards
What is the definition of Anaemia and features of presentation - including those relating to compensation
Haemoglobin lower than normal for the age and sex of patient
Compensation for reduced O2 delivery capacity:
-increased cardiac stroke volume and tachycardia
+ right shift in O2 dissociation curve
- Features:
- can be assymptomatic however eventually
- SOB, fatigue, pallor (conjunctiva, palm creases)
- then congestive HF if severe enough.
How does levels of Hb differ at different stages of life and between f/m
Hb is high at birth and then drops off sharply from 3m - 1 yr old, after which it increases until ~15yrold
Men have higher resting Hb than women. Pregnant women have lowest
What are the 2 approaches to classifying anaemia
+ 3 things related to each one
- Morphological: based on
- RBC appearance under microscope (blood film)
- mean (1) cell volume (bigness)
- mean cell haemoglobin concentration
2. Pathogenetic: based on cause: - Impaired production - blood loss - haemolysis (excess destruction)
What are the other blood tests that help to differentiate anaemias
- > low suggests bone marrow deficiency??
- Hb in g/L ->
- Red cell count
- Haematocrit/packed cell volume (% of RBC compared to blood volume)
- Iron studies
What are the main causes of Impaired production of RBC - and give eg
- Deficiency of substances essential for RBC production
- iron, vit B12, folate - Genetic defect in production
- thalassaemia - Failure of bone marrow: .WBC and platelet count also low
- eg. infiltration of leukaemia, irradiation or drug damage
What are the main causes of Losing RB ->Haemolysis of RBC / haemolytic anaemia
- Blood loss: acute from trauma/surgery
- Haemolysis: shortened survival within the body,
- environment/extrinsic: autoimmune destruction of RBC
- intrinsic problem - eg. inherited defect in RBC structure/ function
eg. G6PD deficiency, hereditary spherocytosis
What are the 3 morphological anaemias
- Microcytic hypochromic anaemia (pale=less Hb, MCV <76)
- Normochromic normocytic anaemia (normal)
- Macrocytic anaemia (MCV>96). most of them normochromic.
What is the 3 main causes of microcytic anaemia
2 is generally mild
Anything that reduces RBC production so less Hb
Haem production:
1. Iron deficiency
- Chronic illness - eg. rheumatoid arthritis, osteomyelitis.
- Underlying inflammation/infection causes block of iron release from macrophages to protect against bacteria growth
This is normochromic- mild hypochromic, and only mild anaemia 90-100g/L
Globin production:
3. Genetic: eg. Thalassaemia (no globins)
What is measured to diagnose Iron deficiency
- Serum iron
- Serum ferritin: soluble storage form of iron
- Iron binding capacity (transferrin- iron transport protein)
- Iron saturation: - amount of iron bound to transferrin
How do you differentiate true iron deficiency from iron block in anaemia of chronic illness using iron measures
In true iron deficiency - transferrin/ unbound iron binding capacity is upregulated via loss of negative feedback so
- high UIBC: serum iron
- Serum ferritin is also very low
In chronic illness/iron block
- serum iron is low-normal so can negative feedback to
- transferrin (low normal) so
- UIBC: serum iron normal
- Normal/raised serum ferritin
- Normal saturation
Is anaemia a late or early stage of iron deficiency
late
What are the causes of true iron deficiency and what are the most likely for premenopausal females, children, post menopausal/men
- Reduced intake from diet: eg. vegetarian
- Malabsorption: from proximal small bowel
- Increased demands: pregnancy
- Chronic blood loss from GI or GU tract
Premenopausal: imbalance between dietary intake and menstrual blood loss
Post/men: occult blood loss from GI tract/ other sites (tumour)
Children: deficient diet
What are the treatments available for iron deficiency and what would the blood film look like in someone on it
Replacement therapy
- oral tablet: ferogradumet (Gi toxicity causing diarrhoea/constipation so adherence poor)
IV infusion: ferric carboxymaltose
The Hb conc increases ~20g/L every 3 weeks so blood film would look dimorphic - old bad cells with good new ones + have more reticulocytes
How is thalassaemia diagnosed and what is the difference between minor and major
- Haemoglobinopathy screen:
a) blood film: fragmented, irregular shaped, small, microcytic RBC
& other blood test values for anaemia
b) iron studies
c) phenotypic analysis: splenomegaly, hepatomegaly, expansion of bone marrow, jaundice
2. Genetic testing
Het: mild anaemia which looks like iron deficiency
Homo: severe anaemia bc both alpha or beta chains reduced/absent depending on alpha or b thalassaemia
What are the 6 causes of macrocytic / megaloblastic anaemia - 2 main ones
Why does it cause anaemia?
- B12 deficiency
- Folate deficiency
B12/Folate involved in DNA synthesis causing abnormal maturation and growth of RBC - not Hb deficiency. May affect all cell lineages if severe
Also
- liver disease
- heavy alcohol abuse
- primary bone marrow disorders
- hypothyroidism
