Thrombocytopenia

Question 1

Causes of thrombocytopenia

Answer 1

Decreased production

• BM dysfunction
• Drugs
• Megaloblastic anaemia
• Inherited platelet disorders

Increased destruction and consumption

• ITP
• Alloimmune
• Drugs
• HITTs
• DIC
• TTP
• Hypersplenism
• Malaria
• Snake venom

Question 2

ITP pathogenesis and presentation

Answer 2

Antibody mediated destruction of platelets by the liver and spleen

F»>M
May present with mucocutaneous bleeding
Isolated thrombocytopenia

Associated with AIHA, CLL, SLE and RA, HCV

Question 3

ITP management

Answer 3

Aim to maintain platelets >30

Prednisone
IVIG

Splenectomy

Romiplostim - TPO receptor agonist
Eltrombopeg - TPO mimetic

Immunosuppression

Question 4

DIC pathogenesis

Answer 4

Thrombocytopenia and abnormal coagulation profile

• Increased PT and ApTT
• Reduced fibrinogen
• High D-dimer

Fibrin deposition
Microvascular dysfunction
Consumption of platelets and coagulation proteins with increased bleeding risk

Question 5

DIC management

Answer 5

Identify and manage underlying cause

Bleeding:

• Platelet transfusion
• FFP
• Cyroprecipitate

Question 6

HITTS Pathogenesis

Answer 6

Caused by formation of IgG antibody that recognises heparin-PF4 complexes

Heparin-PF4 complexes bind to platelet surfaces –> platelet activation and consumption

PROTHROMBOTIC STATE

Develops 5-14 days after exposure to heparin
Platelets fall by >50% rarely <15
High risk of thrombosis

Question 7

HITTS diagnosis and management

Answer 7

HIT pretest probability

Immunoassay to detect HIT antibody that binds PF4
Functional assay - serotonin release assay or heparin induced platelet aggregation

Cease heparin
Direct thrombin inhibitor or Xa inhibitor
Avoid warfarin

Question 8

Thrombocytopenia in pregnancy

Answer 8

Gestational thrombocytopenia - platelets >80

ITP in pregnancy

HELLP