9. Disorders of Haemostasis Flashcards
4 things causing defective haemostasis
- abnormalities in vasc system
- thrombocytopenia
- thrombocytopathy (disordered platelet function)
- defective coagulation
what is most sever disorder
coagulation disorder
bleeding can be into joints and soft tissues
characteristics of vascular bleeding disorders
- easy bruising
- spontaneous bleeding from small vessels
main type of inherited vascular disorder
hereditary harmorrhagic telangiectasia (HHT)
what type of genetic defect is HHT
autosomal dominant
so effects men and women equally
what happens in people with HHT
arterovenous malformations
(connection between arteries and veins will bypass the capillaries)
symptoms of HHT
- telangiectases on nose, tongue, lips = vry common)
- nosebleeds
- GI blood loss (bit more rare) = can lead to chronic iron deficiency
when and what treatment used for HHT
if small blood loss, then no intervention needed
otherwise:
- embolisation = introducing artificial blood clot
- laser treatment to fuse vessels
- tranexamic acid
3 types of vascular purpura
- purpura simplex
- senile purpura
- infection associated purpura
when can infection associated purpura be lethal
whne in unvaccinated individuals
viruses like measles can damage blood vessels around brain or organs
thrombocytopenia meaning
deficiency in plateley numbers
lower than 150x10^9/L
3 main causes of thrombocytopenia
- failure of platelet production (most common)
- increased destruction of platelets
- sequesteration of platelets
what might cause failure on platelet productio
usually bone marrow failure
- aplastic anaemia
or
- leukemia
(2 things that can cause the bone marrow failure)
- drug/viral toxicity
How can we diagnose thrombocytopenia
- clinical history
- peripheral blood count
- blood film
- bone marrow exam
main cause of increased destruction of platelets
autoantibodies attaching to platelet surface
(so some kind of autoimmune disease)
main type of autimmune disease causing destruction of platelets
Idiopathic thrombocytopenia purpura (ITP)
can be CHRONIC or ACUTE
people who usually get chronic ITP
women 15-50yrs old
what type of antibodies attach onto platelets in chronic ITP
IgG
acts against glycoprotein IIb/IIIa or Ib
who does acute ITP usually affect
children under 10
what might trigger acute ITP
abrupt onset after vaccination
or viral infection e.g. after chicken pox, measles
how might post viral cause acute ITP
IgG antibody can attach to viral antigen thats absorbed onto the platelet surface
consequences of acute ITP
usually spontatneous remission
minority of cases will develop chronic ITP
name of disease that causes sequestration of platelets
splenomegaly
what can splenomegaly cause
goes from usual 30% in spleen up to 90%
= leads to thrombocytopenia
what might splenomegaly be caused by
leukemia
- over production of cells
- ends up in spleen
= leads to enlarged, palpable spleen
what is thrombocytopathy
disorder of plateley function
(will have NORMAL platelet count)
what 2 types of thrombocytopathy disorders are there
inherited and acquired
(inherited much more rare)
2 ways thrombocytopathy can be acquired
- antiplatelet drugs
- haematological malignancy
what drug may cause thrombocytopathy
aspirin
how can spirin inhibit platelet aggregation
- irreversibly inactivates cyclooxygenase (COX)
- which usuallly oxygenates arachindonic acid to thromboxane A2
what do we need to check for before aspirin
obvs other stuff too
but need to make sure they dont already have a low platelet count
what 2 types of haematological malignancy can affect platelet function
- acute myeloid leukemia
- any myeloproliferative disorders and myeloma
diagnosing platelet disorders
- clinical history
- initial blood count and blood film exam
- bone marrow biopsy
- bleeding time
what might a bone marrow biopsy be used for
thrombocytopenic patients
detect malignancy (failure of platelt production)
if blood count is in normal limits then what might be done
tests to detect abnormal platelety function
