L13 - Coagulation and Haemophilia Flashcards
1
Q
Haemostasis
A
• A complex process involving:
- Platelets
- Plasma proteins
- Endothelial cells
- Smooth muscle cells
•Keeps the blood fluid while ensuring that blood loss is minimised at a site of vessel injury
2
Q
Old theories of blood coagulation
A
- Cooling
- Blood clotted when it cooled
- Rest
- Motion inhibited clotting, rest encouraged it
- Vital Force
- Blood was alive in blood vessels and died outside them
- Air
- Exposure to air (either oxygen or nitrogen) caused the blood to clot
3
Q
Prothrombin Time
A
- Plasma (100 µL)
- Normal (control) or patient plasma
- Thromboplastin - 200 µL (Tissue factor, phospholipids, calcium (0.025 M))
- Reactions proceed through extrinsic/common pathways
- Generates fibrin (clot)
- Record clotting time (1 decimal place)
- Clotting factor deficiencies (VII, X, V, II, I)
- Monitor oral anticoagulant therapy (warfarin)
4
Q
Partial Thromboplastin Time
A
- Plasma (100 µL)
- Partial Thromboplastin (Phospholipid -100 µL)
- Activator (100 µL) -negatively charged e.g. kaolin
- Incubate for 3 minutes
- Calcium chloride (0.025 M) (100 µL)
- Reaction proceeds through intrinsic/common pathways
- Generates fibrin clot -record clotting time (1 d.p.)
- Clotting factor deficiencies (I, II, V, VIII, IX, X, XI, XII)
- Monitor anticoagulant therapy (UF heparin)
5
Q
Normal PT, Prolonged aPTT
A
- Extrinsic and common pathways are normal
* Deficiency in intrinsic pathway (Factor VIII, IX, XI, or XII)
6
Q
Prolonged PT, Normal aPTT
A
- Intrinsic and common pathways are normal
* Deficiency in extrinsic pathway (Factor VII)
7
Q
Prolonged PT, Prolonged aPTT
A
- Deficiency in common pathway (Factor X, V, Prothrombin, Fibrinogen)
- Deficiency in multiple coagulation factors
8
Q
Pattern of inheritance of haemophilia
A
- Males were affected by the disease
* Females were vary rarely affected, but they could pass the disease onto their offspring (carriers)
9
Q
Those affected from haemophilia suffered from bleeding into:
A
- Muscle/soft tissue
- Brain
•Joints were involved (? Arthritis)
10
Q
Haemophilia A
A
deficiency of Factor VIII
11
Q
Haemophilia B
A
deficiency of Factor IX
12
Q
Incidence of haemophilia in males
A
1:5000 –1:25 000 male births
13
Q
Haemophilia as an X-linked, recessive disease
A
- Females that carry the mutation are called ‘carriers’
- Carriers have a 50% chance of passing the mutation onto their sons
- Male haemophiliacs will pass the mutation to their daughters, while their sons are unaffected
- 1980’s -Both Factor VIII and IX genes were cloned and found to reside on the long arm of the X-chromosome
14
Q
Haemophilia in females (rare cases):
A
- Offspring of a male haemophiliac and a female carrier
- Occurrence of two factor VIII gene mutations
- Extreme Lyonisation (or X-inactivation)
15
Q
Lab diagnosis of haemophilia
A
•Mixing studies
- Mix an equal volume of patient plasma with normal plasma
- Perform an aPTT
- If the patient has a factor deficiency, the missing factor is replaced by the same factor that is present in the normal plasma
- The aPTT is corrected back to normal (i.e. normalized)
•Factor assays to determine the concentration of FVIII and FIX present in the patient plasma
16
Q
Haemophilia Clinical Manifestations in newborns
A
- Bleeding at the umbilical stump
- Bleeding after circumcision
- Bleeding with heel pricks/immunisation
- Rarely, newborns will present with severe bleeds
- Bleeding in infants often does not occur until they become mobile
17
Q
Development of haemophilia joint disease
A
- An acute bleed into the joint increases pressure within the synovial cavity
- Recurrent bleeding causes chronic synovitis and damage to the cartilage and bone, → haemarthrosis
- Haemarthrosisoccurs in three stages
18
Q
Stages of haemoarthosis
A
- Acute haemarthrosis
• Bleed into the joint - Chronic synovitis
• Iron (from lysed RBCs) promotes the production of inflammatory cytokines
• Synovium becomes vascular and inflammatory cells are recruited
- Degenerative arthritis • Exposure of blood and cytokines to the cartilage results in its destruction
19
Q
Pseudotumours
A
- A clinical manifestation of haemophilia
* Large encapsulated haematomas in large muscle groups and some bones
20
Q
Intracranial haemorrhage
A
- Can occur in the neonatal period (3-5% of haemophiliacs)
* Childhood and adult ICH usually occurs after trauma
21
Q
Treatment of haemophilia
A
- Early “treatments”
- Russell’s Viper Venom
- Blood transfusion
- Fresh Frozen Plasma (FFP)
- Cryoprecipitate
- Factor VIII and IX concentrates
- Haemophilia Treatment Centres –early 1970’s
22
Q
Early “treatments”
A
• Administration of lime, O2, use of thyroid gland, bone marrow, H2O2, gelatin etc.
23
Q
Russell’s Viper Venom
A
• Used in the 1930’s for “local” applications
24
Q
Blood transfusion
A
- First documented case for the treatment of haemophilia was in 1840
- Not accepted as a routine treatment until the 1940’s
25
Fresh Frozen Plasma (FFP)
* Used for treatment in the 1950s/1960s
* Recipient required hospitalisation
* Required large volumes
26
Cryoprecipitate
* Prof Judith Pool discovers that, if FFP is allowed to slowly thaw in the cold, a precipitate forms. This can be collected by centrifugation and the remaining plasma recombined with the remaining blood
* The precipitate, called cryoprecipitate, contains FVIII and fibrinogen and can be stored frozen
* Allowed injection of concentrated FVII
27
Factor VIII and IX concentrates
* Late 1960’s –methods to purify fVIII and fIX from plasma were described
* Allowed the production of fVIII and fIX concentrates
* Large volumes of plasma were pooled from multiple donors to make one batch of concentrate
* Early 1970’s –factor concentrates were available for home use
28
Blood related discoveries in the late 1970s/1980s
* 1984 –HIV was identified
* 1985 –HIV testing in blood facilities implemented
* 1989 –Hepatitis C was isolated
* 1990 –Hepatitis C testing of blood donors began
* Was estimated that 50% of haemophiliacs succumbed to viral infection
29
Recombinant factor treatments 1980s/1990s
* 1982 –factor IX was cloned
* 1984 –factor VIII was cloned (These important discoveries allowed the production of recombinant fVIII/fIX protein)
* 1992 –recombinant fVIII was licensed for the treatment of haemophilia A
* 1997 –recombinant fIX was licensed for the treatment of haemophilia B
30
On-demand treatment regimes
* Affected individuals are treated with replacement factor only when a bleeding episode begins
* Does not prevent bleeding episodes from starting
31
Prophylactic treatment regimes
* Affected individuals are treated with replacement factor 1-4 times a week
* Achieves a basal level of factor that maintains haemostasis (~30%)
* A significant amount of factor is used
32
Life expectancy of haemophilia by the 1980’s
* Before the advent of cryoprecipitate, males rarely lived to reproductive age. The average life expectancy was 11 years.
* by 1980s this was increased to 50-60 years
* Use of factor concentrate had a significant effect
33
Life expectancy of haemophilia today
* Normal life expectancy
* Use of recombinant factor and prophylactic treatment
* Death from other causes (i.e. cardiovascular disease etc)
34
Future treatment of haemophilia
Gene therapy:
* Recent studies have investigated the use of gene transfer to insert a normal VIII/IX gene into affected individuals
* Factor IX gene is put into a vector which targets the production of factor IX protein to the liver
* Maintains FIX at 1-6% of normal in individuals with severe haemophilia B
* Decreases the amount of factor IX concentrate used
* Decreases the number of bleeding episodes
35
Royal family haemophilia
* It was hypothesised that those affected by Haemophilia in the Royal Family had Haemophilia A
* In 2009, it was reported that the remains of all Russian Royal Family members were found
* They found that there was no mutation in the factor VIII gene (F8), but there was one in IX gene
* Therefore, the Royal Family had haemophilia B
