Thrombocytopenias and Thrombocytosis Flashcards
What is thrombocytopenia?
Low platelets
This is caused by reduced platelet production in the bone marrow, excessive peripheral destruction of platelets or sequestration in an enlarged spleen
What classes can the causes of thrombocytopenia be divided into?
- Impaired production
- Excessive Destruction/increased consumption
- Sequestration
- Dilutional
What are causes of impaired production which leads to thrombocytopenia?
- Selective megakaryoctye depression
- Bone marrow failure
- Myelodysplastic syndromes
- Myeloma
- Myelofibrosis
- Solid tumour infiltration
- Aplastic anaemia
- HIV infection
What are causes of excessive destruction or increased consumption which can lead to thrombocytopenia?
- Autoimmune - ITP
- Drug induced
- Post-tranfusion purpura
- DIC
- Thrombotic thrombocytopenia purpura
What are causes of sequestration of platelets leading to thrombocytopenia?
- Splenomegaly/Hypersplenism
What are causes of dilutional thrombocytopenia?
Massive transfusion
If thrombocytopenia was caused by a something which impaired production, how would you treat it?
- Treat the cause
- If platelets are critically low - platelet tranfusion
What is immune thrombocytopenic pupura?
Thrombocytopenia is due to immune destruction of platelets. The antibody-coated platelets are removed following binding to Fc receptors on macrophages.
What age range does ITP present in children?
2-6 years old
What can precipitate the development of ITP in children?
Infection - recent viral infection, including varicella zoster or measles
How soon after infection can ITP present in children?
Approx 2 weeks after infection
What are features of acute ITP?
Common
- Easy bruising
- Purpura
- Epistaxis
- Menorrhagia
Rare
- Major haemorrhage
Does someone with ITP typically present with splenomegaly?
No - extremely rare
Which sex is ITP characteristically seen in adults?
Females
What is the overriding feature of chronic ITP?
Fluctuating course of bleeding, epistaxis etc.
What investigations would you perform if you suspected ITP?
- Bloods - FBC, PT, APTT, Clotting Factors, Thrombin time, bleeding time
- Bone marrow aspirate
What might you find on investigation for ITP?
- Thrombocytopenia
- Megakaryocytes on bone marrow
How would you manage someone with ITP?
Aim to keep platelets >30x109/L
- If mild - nothing
- If platelets < 20x109/L - prednisolone 1mg/kg/d, then reduce after remission
- If pred fails - immunosuppression
What is thrombotic thrombocytopenia?
TTP is a rare, but very serious condition, in which platelet consumption leads to profound thrombocytopenia. It appears to be due to platelet aggregation by very high molecular weight multimers of von Willebrand factor. Such multimers are normally secreted by endothelial cells but are rapidly degraded into smaller multimers.
In all forms of TTP there is deficiency of ADAMTS 13 - the protease that rapidly degrades these multimers.
What are features of TTP?
Symptom complex
- Florid purpura
- Fever
- Fluctuating cerebral dysfunction
- Microangiopathic haemolytic anaemia
- Renal problems
What are secondary causes of TTP?
- Pregnancy
- Oral contraceptives
- SLE
- Infection
- Drug treatment
What might you find on investigation for TTP?
- Normal coagulation screen
- Increased LDH
What investigations would you perform if you suspected TTP?
- Bloods - FBC, PT, APTT, Clotting Factors, Thrombin time, bleeding time, LDH
- Bone marrow aspirate
How would you manage someone with TTP?
- Plasma exchange - provides a source of ADAMTS-13 and removes associated autoantibody in acute TTP
- Methylprednisolone - acutely
What is thrombocytosis?
Where platelet count rises above 400 × 109/L
What are causes of thrombocytosis?
- Splenectomy
- Malignant disease
- Inflammatory disorders - RA, IBD
- Major surgery
- Post haemorrhage
- Myeloproliferative disorders
- Iron deficiency.
Which part of the immune response does thrombocythaemia occur in conjunction with?
Acute-phase
What deficiency is present in TTP?
ADAMTS 13
