Anaemias - macro and microcytic Flashcards
What does anaemia mean?
What are the tresholds for this in men and women?
Reduced ability to deliver oxygen due to a lower number of RBCs or a decreased amount of haemoglobin.
Men Hb < 130 g/ml
Women Hb < 120g/ml
What are the three main mechanisms of anaemia? + examples of each?
Blood loss - Trauma or GI bleeding
Decreased RBC production - IDA, B12 deficiency, Thalassaemia, Malignancy
Increased RBC destruction - Haemolytic anaemia
How can anaemia be classified?
Microcytic
Normocytic
Macrocytic
What are the main differentials in a microcytic anaemia? Hence what Ix are important?
IDA
Thalassaemia
Sideroblastic anaemia
Ix:
- Peripheral blood smear
- Iron Studies
What is the most common cause of IDA?
Occult blood loss
What are the findings of IDA on:
Peripheral blood smear
Iron studies
FBC
Peripheral blood smear:
- Pencil cels
Iron studies:
- Low iron
- Low ferritin (storage marker for iron hence low)
- High transferrin (compensatory rise - made in liver, may be low in liver disease)
- Raised TIBC (rises when iron needs to be maintained by body)
FBC:
- Reactive thrombocytosis
Describe the realationship between ferritin and transferrin?
Ferritin stores iron and releases it in a controlled fashion
Serum Transferrin increases in IDA, as the liver increases transferrin production to bind to as much available iron it can to compensate for low iron levels
NB: in liver disease transferrin can be low
Mx of IDA?
Investigate underlying cause, iron supplementation
What conditions can show ‘pencil cells’ on peripheral blood smear?
IDA, Thalassemia and PK deficiency
What are the different types of thalassaemia?
a-thalassaemia
b-thalassaemia
thalassaemia trait (can be a- or b-)
What are the key ix findings of thalassaemia?
Peripheral blood smear:
- Basophillic stippling (aggregation of ribsomal material in cytoplasm - seen as purple dots in rbcs)
- Target cells (RBCs with a central area of staining)
Iron studies:
- Iron, ferritin, transferrin and TIBC = All normal
What conditions can show target cells on peripheral blood smear?
Thalassaemia, hyposplenism, hepatic failure, haemoglobinopathies
What poisoning can cause basophillic stippling as well (as in thalassaemia)?
Lead poisoning
Mx of thalassaemia?
Iron supplementation, regular transfusions, iron chelation
What are the levels of Hb, serum iron, TIBC / Transferrin, transferrin saturation and ferritin in:
IDA
Anaemia of Chronic Disease
Thalassaemia trait
IDA:
Hb - Low
Serum iron - Low
Ferritin - Low
TIBC / Transferrin - Raised
Transferrin saturation - Low
Anaemia of Chronic Disease:
Hb - Low
Serum iron - Low
Ferritin - Normal or High (in acute phase)
TIBC / Transferrin - Normal / Low
Transferrin saturation - Normal
Thalassaemia trait:
Hb - Normal / low
Serum iron - Normal
Ferritin - Normal
TIBC / Transferrin - Normal
Transferrin saturation - Normal
What is sideroblastic anaemia? How can this be caused
Sideroblastic anemia: iron is available but the body cannot incorporate it into hemoglobin.
This forms iron laden mitochondria
This can be congenital or accquired (alcohol, lead poisoning)
Key features in Ix of sideroblastic anaemia?
Peripheral blood smear – basophilic stippling
Iron studies – ↑iron, ↑ferritin, ↓transferrin, ↓TIBC
Bone marrow – ringed sideroblasts
Mx of sideroblastic anaemia?
Treat underlying cause, regular transfusions
What are some key differentials to be considered in macrocytic anaemia? Hence what ix should be offered?
Megaloblastic anaemia: vitamin B12 deficiency, folate deficiency
Non-megaloblastic: Alcohol, Hypothyroidism, pregnancy
Key investigations
- Peripheral blood smear
- LFTs
- TFTs
How can alcohol and hypothyroidism cause a macrocytic anaemia?
Alcohol - Deposition of cholesterol into erythrocyte membranes causing their SA to rise (raised MCV)
Hypothyroidism - Thyroxine important of EPO production hence without it -> anaemia
What are the dietary sources of B12 and Folate?
Vitamin B12: meat, fish, eggs, dairy products
Folate: leafy green vegetables, such as cabbage and kale.
How to differentiate between the different causes of megaloblastic anaemia?
Duration – months for folate deficiency, years for vitamin B12 deficiency
Clinical findings – vitamin B12 deficiency associated with neurological changes
Serum methylmalonic acid – elevated in vitamin B12 deficiency
Schilling test – positive in vitamin B12 deficiency 2º to pernicious anaemia (not really used much anymore)
Drug history – phenytoin inhibits folate absorption
Which type of anaemia is methylmalmonic acid elevated in and why?
Megaloblastic anaemia due to B12 deficiency
Methylmalonic acid is converted to succinyl-CoA using vitamin B12 as a cofactor
Vitamin B12 deficiency, therefore, can lead to increased levels of serum methylmalonic acid
How to tell the difference between the different causes of non-megaloblastic anaemia?
Causes: Alcohol, hypothyroidism, pregnancy
History – features of hypothyroidism
Clinical findings – hepatomegaly, gynaecomastia, abdominal veins, ascites, jaundice
LFTs – ↑AST, ↑ALT, ↑GGT, AST:ALT >2:1 (alcoholic)
TFTs – ↑TSH, ↓T3/T4, anti-thyroid peroxidase antibodies
