Heritable bleeding disorders Flashcards
1
Q
Haemostasis
A
- Haemostasis exists in a balance between bleeding and clotting
2
Q
Breech of vasointegrity =
A
- Initial vasoconstriction, then activation of platelets at the site of vascular injury = adhere to the area of damaged vessel become activated and aggregate to form a plug
- Coagulation is then activated, and a fibrin plug is formed
3
Q
glycoprotein 1b9
A
- receptor for vWF
4
Q
Extrinsic pathway of coagulation cascade
A
- Activated first
- Exposure of tissue factor, binds + activates factor V11
- Factor V11a activates factor X
- Xa + Va cleaves prothrombin to produce thrombin
- formation of fibrin from fibrinogen
5
Q
Intrinsic pathway of coagulation cascade
A
- Involved when blood gets into contact with a foreign surface
- When thrombin is generated it feedbacks and directly activates factor XI
6
Q
Common pathway
A
Where the intrinsic and extrinsic pathways of the coagulation cascade interact.
- can’t get fibrin without activation of Factor X
7
Q
Fibrinolysis
A
- Plasma proteins circulate and become active when required
- plasmin breaks down cross-linked fibrin into fibrin degradation products
- Plasmin is generated by the action of tissue plasminogen activator on inert plasminogen
8
Q
Bleeding disorder types
A
- Congenital – usually single gene defect
- Acquired – often multiple defects
- Platelet/vessel wall defect - mucosal and skin bleeding - easy bruising, petechial rash, heavy periods, nose/gum bleeds.
- Coagulation defect – deep muscular bleeds, following trauma
9
Q
What to ask when taking a history of a patient with bleeding
A
- Ask about previous bleeding
- Response to challenges
- Severity of bleeding
- Systemic illness
10
Q
Appropriate investigations for patients with bleeding
A
- Firstly - FBC and blood film
- Coagulation screen and Clauss fibrinogen
- Prothrombin time (PT) = measuring extrinsic pathway, APTT = measuring intrinsic pathway
- vWF profile
- If all normal and suspicion remains – FXIII assay and assay of alpha2anti-plasmin
11
Q
A coagulation screen includes the following tests
A
- Prothrombin Time (PT)
- Activated Partial Thromboplastin Time (APTT)
- Fibrinogen
12
Q
Normal coagulation screen results
A
- Prothrombin Time (PT) = 10–14 seconds
- Activated Partial Thromboplastin Time (APTT) = 22–36 seconds
- Clauss Fibrinogen = 1.5–4.5 g/l
13
Q
Platelet/vessel wall defects
A
- All give rise to prolonged bleeding time
- Abnormal vessel walls due to scurvy
- vWD - abnormal interaction between platelets and cell walls
14
Q
Children with meningococcal meningitis get what?
A
- Will get petechial rash, often because their blood platelet count drops and/or platelets are not working normally
15
Q
Von Willebrand Disease - 3 types
A
Type 1 = reduced production of normal molecule = deficiency of protein = milder bleeding disorder – MOST COMMON BLEEDING DISORDER, F=M
- Type 2 = normal amount of abnormal molecule = still a mild disease but more manifestations than type 1
- Type 3 = absence of molecule = severe
