Thrombocytopenia

Low Platelet Count

1) Decreased production from bone marrow

2) Peripheral destruction/consumption

- autoimmune (reticuloendothelial system)

- massive clotting process (DIC)

Ix of Choice
Bone marrow examination

Underproduction
1) BM infiltration - leukaemia/secondary malignancy
2) Decrease in megakaryocyte numbers/abnormal differentiation - aplastic anaemia/severe megaloblastic anaemia/excess alcoholism

Peripheral Destruction/Consumption
BM: megakarocytes no. normal or raised

1) Raised peripheral destruction

Pathology
Immunological
aB adh to Plt membranes
Premature ret-end Plt clearance

Aetiology
*ITP (idiopathic thrombocytopenia purpura)
2ry -
SLE
Lymphoid malignancies (B cell chronic lymphocytic leukaemias)
Drugs (quinine, rifampicin)

Ix
Plt a/ Ig (aBs bound to plt surface antigen)

2) Increased consumption

Haemostasis

DIC
Tcytopen assoc with consumption of all clotting Fx
Prolonged coag time
Intravascular haemolytic An
RBCs chopped up by fibrin strands

3) Pooling

1/3 plts pooled in normal spleen
Mod-severe splenomegaly = 'circulating thrombocytopenia'
eg myelofibrosis + mass spleen

4) Massive Transfusion
Bank blood = no functional platelets
Clumps of dead WCCs + plts = microaggregates
Plt adh (before ret-end/lung filtration)
Solution: microaggregate filter in giving set

NB + plt consumption in bleeding site/wound loss