Thrombocytopaenia Flashcards
What are platelets?
Anucleate cells. Lifespan 7-10 days. Controlled by thrombopoietin (TPO) produced in liver.
Bleeding problems can be due to either reduced platelet numbers or reduced platelet function.
What is the range of normal platelet count?
Normal platelet count is between 150 to 450 x 10^9/L.
What is thrombocytopenia?
Not enough platelets.
Give 2 causes of thrombocytopenia.
- Decreased production
- Increased destruction
Platelet dysfunction: what can cause decreased platelet production?
- Congenital causes e.g. malfunctioning megakaryocytes.
- Infiltration of bone marrow e.g. leukaemia, lymphoma, myeloma.
- Reduced production from BM e.g. alcohol, reduced TPO
- Infection e.g. HIV/TB.
Platelet dysfunction: what can cause increased platelet destruction?
- Autoimmune e.g. ITP.
- Hypersplenism.
- Drug related e.g. heparin induced.
- Consumption of platelets - DIC and TTP.
Platelet dysfunction: what can cause reduced platelet function?
- Congenital abnormality.
- Medication e.g. aspirin.
- VWF disease.
- Uraemia.
What is ITP?
Immune Thrombocytopenia Purpura.
Isolated thrombocytopenia thought to be due to anti-platelet autoantibodies, leading to the immune destruction of platelets in spleen - autoimmune disorder.
What antibodies are often found in ITP?
IgG.
What are 3 other names for ITP?
- Autoimmune thrombocytopenic purpura.
- Idiopathic thrombocytopenic purpura.
- Primary thrombocytopenic purpura.
ALL mean the same condition!!!
Describe the epidemiology of ITP.
Typically occurs in children w/preceding viral illness or in middle aged women.
What can cause ITP?
- Viral infection.
- Malignancy.
Give 5 signs + symptoms of ITP.
- Easy bruising
- Epistaxis (nose bleed)
- Menorrhagia (heavy menstruation)
- Petechiae / Purpura (red or purple spots on the skin caused by bleeding underneath skin)
- Gum bleeding
What investigations are carried out to diagnose ITP?
- Bloods - FBC - Thrombocytopenia
- Bone marrow examination:
* Shows thrombocytopenia with increased or normal megakaryocytes in the marrow - Platelet autoantibodies (present in 60-70%) - not needed for diagnosis
How would you manage ITP?
- First line:
1. Corticosteroids e.g. PREDNISOLONE
2. IV immunoglobulin e.g. IV IgG - raises platelet count more rapidly than steroids - thus: useful for surgery - Second line:
3. Splenectomy
4. If splenectomy fails, then immunosuppression e.g. ORAL/IV AZATHIOPRINE
What is TTP?
thrombotic thrombycytopenia purpura
MED EMERGENCY - 95% FATAL. consider in any pt w/haemolytic anaemia + thrombocytopenia.
Describe the pathophysiology of TTP.
- Deficiency of protease that breaks down vWF (ADAMTS-13)
- Large multimers of vWF form resulting in platelet aggregation and fibrin deposition in small vessels
- Widespread platelet adhesion/aggregation
- Leading to microvascular thrombosis + thrombocytopenia + haemolytic anaemia
- Red cells passing these clots rupture due to shear force.
give some causes of TTP. RFs?
congenital
sporadic
autoantibody mediated - pregnancy, SLE, infection
RFs - black, overweight, F, pregnacny
Give 5 symptoms of TTP.
- Florid purpura
- Fever
- Fluctuating cerebral dysfunction
- Coma, Focal neuro, seizures, headaches, confusion - Haemolytic anaemia with red cell fragmentation
- Pallor, jaundice, pruritus - Renal failure / AKI.
- Raised urea/creatinine
Typical pentad of clinical presentation in exam questions
Investigations for TTP.
- FBC
- Low platelets
- Hb <8
- Reticulocyte count raised - LDH + bilirubin raised
- As a result of haemolysis - Peripheral blood smear
- Microangiopathic w/SCHISTOCYTES (RBC fragments) - Urea and Creatinine raised
- Urinalysis
- Proteinuria - Coagulation screen - normal
How would you treat a patient with TTP?
- Plasma exchange (urgent) - within 24 hrs
- To remove antibody to ADAMTS-13 as well as provide a source of ADAMTS-13 - IV METHYLPREDNISOLONE (within 24 hrs)
- Immunosuppression - IV RITUXIMAB
- Antibiotic - Aspirin
- Long term = decreases platelet aggregation
