Exam Cram

• Pathophysiology: autoimmune destruction of ADAMS 13 which regulates platelets

• Presentation: purpura, unwell (often neurology/ confusion), thrombocytopenia, often < 50yrs

• Diagnosis: low ADAMS 13

• Management- call haematology for plasma exchange

Outline

Background 

Adamts 13 molecule reduces the size of von Willebrand Factor

In TTP there is reduced Adamts 13 and hence von Willebrand Factor remains too large. These large von Willebrand factors cause platelets to aggregrate causing large clumps resulting in:

• Arterial and venous clots

• Consumptive thrombocytopenia

• Haemolytic anaemia (clumps shred red blood cells)

Causes: E.coli 0157 Shiga Toxin

Presentation

Pentad: confusion, fever, AKI, thrombocytopenia, haemolytic anaemia

History:

• Confusion, drowsy

• Pregnancy association

Examination:

• Febrile 

• Petechial rash

• Focal neurology

Investigations

• Blood film: haemolytic anaemia, 

  • • Fragmented red cells

    • Low haptoglobin

    • Schistocytes

• Thrombocytopenia

• Cr 190

• Low ADAMTS-13

Diagnosis

Diagnostic criteria:  low ADAMS 13, < 10%

Differentials (thrombocytopenia)

• Acute haemolysis and thrombocytopenia: 

  • • • • Ecoli HUS: Severe abdo pain/ diarrhoea, severe AKI

        • DIC: Abnormal coag

• Thrombocytopenia:

  • • • • ITP: No neurology and usually well

Management

• Haematology referral 

• Plasma exchange (plasmaphoresis)

Haem Reg Notes

Management II

• Plasma exchange improves the survival rate from 5% to 80%. 

• Platelet transfusions are contraindicated

• Consider steroids, FFP, RBC and IVIg

• Rituxumab under specailaist approval

References and resources

Written in 2025