Abnormal Platelet Function

Platelets count = normal
BT = prolonged

CFx
Purpura/bleeding mucosa

Aetiology
Congenital
Acquired

Acquired
1) *Drugs (asp/NSAIDS) - NB - stop for 2 weeks and repeat BT
2) Membrane defects (CRF/polycythaemia/raised FDPs)
3) Acquired storage pool disease (myeloproliferative D/Os eg essential thrombocythaemia)

Congenital
Rare
1) Membrane abnormal (Bernard-Soulier Syndrome = deficiency in glycoprotein Ib)
2) Glanzmann's Thromboasthenia (deficiency of gp IIb/IIIa)
3) Arachadonic acid metabolism enzyme defects (cycloxygenase deficiency)
4) Storage Pool Disease (Abn/decreased alpha &/ dense granules)

Ix
i) Plt aggregation studies (ristocetin, ADP, collagen)
ii) ADP & ATP (contents of alpha and dense granules) release post max-stim
iii) Quantify specific membrane protein receptors (*gp Ib & gp IIb/IIIa)
iv) Ix arachadonic acid pathway & Ca flux
v) exclude immunological destruction (plt a/ Ig)

Tx
1) Underlying cause
2) Congenital = plt concentrates (operations/bleeding)
OR DDAVP infusion *storage PD
3) ITP
- Steroids (pred) - suppress immune reaction & inhibit splenic sequestration
- Splenectomy - decrease plt destruction
- HD IV human gammaglobulin (temporary ret-endothelial blockade)
Clinical Course
Post-splen = 60% remission
NB Proph. pneumococc. vacc & long-term penicillin
If splenectomy/steroidx ineffective - other immune suppressants eg azathioprine