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Summary Haematology overview
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Overview of the key conditions within haematology that medical students need to know for finals.
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HaematologyPre-clinical................................................................................................................................................2
Haemostasis..........................................................................................................................................................2
Haematopoiesis.....................................................................................................................................................2
Coagulation screen and blood film interpretation.....................................................................................3
Sickle cell disease......................................................................................................................................5
Acute intermittent porphyria....................................................................................................................7
Anaemia...................................................................................................................................................7
Microcytic anaemia................................................................................................................................................8
Iron deficiency anaemia................................................................................................................................................................8
Thalassaemia.................................................................................................................................................................................9
Sideroblastic anaemia.................................................................................................................................................................10
Normocytic anaemia............................................................................................................................................10
Anaemia of chronic disease........................................................................................................................................................10
Aplastic anaemia.........................................................................................................................................................................10
Macrocytic anaemia.............................................................................................................................................11
Folate deficiency.........................................................................................................................................................................11
B12 deficiency.............................................................................................................................................................................11
Haemolytic anaemia............................................................................................................................................12
Blood presentations................................................................................................................................14
Neutropenia.........................................................................................................................................................14
Neutrophilia.........................................................................................................................................................15
Pancytopenia.......................................................................................................................................................16
Thrombocytopenia...............................................................................................................................................16
Thrombophilias.......................................................................................................................................17
Inherited thrombophilias.....................................................................................................................................18
Antithrombin III deficiency.........................................................................................................................................................18
Protein C and S deficiency..........................................................................................................................................................18
Factor V Leiden mutation...........................................................................................................................................................18
Prothrombin 202010 A mutation...............................................................................................................................................19
Acquired thrombophilias.....................................................................................................................................19
Paroxysmal nocturnal haemoglobulinuria..................................................................................................................................19
Antiphospholipid syndrome.......................................................................................................................................................19
Myeloproliferative disorders......................................................................................................................................................20
Thrombosis.............................................................................................................................................23
Venous thromboembolism..................................................................................................................................23
Arterial thrombosis..............................................................................................................................................24
Paraproteinaemias.................................................................................................................................24
Congenital bleeding disorders.................................................................................................................25
vWF deficiency.....................................................................................................................................................25
Platelet deficiency................................................................................................................................................26
Haemophilia........................................................................................................................................................26
Acquired bleeding disorders....................................................................................................................26
, Warfarin..............................................................................................................................................................26
Antiplatelet therapy.............................................................................................................................................27
Hereditary haemochromatosis.............................................................................................................................28
Pre-clinical
Haemostasis
Haemostasis – natural process in which blood flow
slows and a clot forms to prevent blood loss during
an injury.
1. Platelet plug formation
2. Coagulation
Platelet plug formation:
Endothelial injury – nerves and SM cells
detect injury. This contraction of blood
vessel. Secretion of NO and prostaglandins
stop and secretion of endothelin begins
further contraction.
Damage to endothelial cells exposes
collagen, and the damaged cells release Von
Willebrand factor which binds to the
collagen.
GP1B surface proteins on platelets bind to
VWF
Platelets change shape, release more VWF,
serotonin, calcium, ADP, thromboxane A2.
ADP and thromboxane A2 GPIIB/IIIA
expression.
GPIIB/IIIA binds to fibrinogen which links
the platelets platelet plug
Coagulation:
Extrinsic pathway – trauma damages blood
vessel, exposes cells under endothelial
layer. Factor III (tissue factor) is embedded
in membrane. Factor VII in the blood binds
to tissue factor VIIa-TF complex
o Measured by PT
Intrinsic pathway – circulating factor XII
contacts negatively charged phosphates on
platelets/subendothelial collagen Factor
XIIa. Factor XIIa cleaves factor XI factor
XIa. Factor XIa (+calcium) cleaves factor IX
IXa. Factor IXa + factor VIIIa (which is
bound to VWF) = prothrombinase complex,
which then enters the common pathway
o Measured by APTT
Vitamin K regulates blood coagulation – converts
coagulation factors into mature forms. Factors 2, 7,
9, 10 require vitamin K.
Haematopoiesis
Haematopoiesis = process of haematopoietic stem cells in BM producing mature blood cells.
In embryos, haematopoiesis occurs in blood islands in the yolk sac, and in spleen, liver and LNs. At around 4-5
months gestation the BM takes over.
Haematopoietic stem cells can form 2 cell lineages.
, Coagulation screen and
blood film
interpretation
Activated partial thromboplastin time
(APTT) – measure of time taken for intrinsic
pathway to occur. Usually 35-40 seconds.
Prothrombin time (PT) – measure of the
time taken for the extrinsic pathways to
occur. INR is a direct measure of PT
(internationally standardised, therefore
used for warfarin checks). Usually 12-13
seconds. INR usually 0.8-1.2.
Thrombin time – test of how fast fibrinogen
is converted fibrin by thrombin. This can
be due to DIC, liver failure, malnutrition,
abnormal fibrinolysis.
Blood clotting results:
Haemophilia - APTT, normal PT, normal bleeding time APTT = intrinsic and
Von willebrand’s disease - APTT, normal PT, bleeding time common pathways
Vitamin K deficiency - APTT, PT, normal bleeding time PT = extrinsic and common
DIC - APTT, PT, bleeding time, platelets pathways
ITP/TTP/HUS - bleeding time and platelets, normal APTT and PT
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