Thrombotic thrombocytopenic purpura

Question 1

Pathogenesis of thrombotic thrombocytopenic purpura (TTP)

Answer 1

large and sticky multimers of von Willebrand’s factor cause platelets to clump within vessels

because deficiency in

TTP there is a deficiency of ADAMTS13 (a metalloprotease enzyme) which breakdowns (‘cleaves’) large multimers of von Willebrand’s factor

Question 2

causes of TTP ?

Answer 2

post-infection e.g. urinary, gastrointestinal

pregnancy

drugs: ciclosporin, oral contraceptive pill, penicillin,

clopidogrel, aciclovir

tumours
SLE
HIV

Question 3

clinical features of TTP ?

Answer 3

fever

fluctuating neuro signs (microemboli)

Scant blood in urine

jaundiced

Question 4

diagnosis of TTP in blood investigations ?

Answer 4

microangiopathic haemolytic anaemia
thrombocytopenia
renal failure
= similar to HUS but no neurolgical signs

blood film - fragmented red blood cells

Question 5

Mx of thrombotic thrombocytopenia purpura ?

Answer 5

plasma exchange is the treatment of choice

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no antibiotics - may worsen outcome