Rare form of thrombotic microangiopathy characterised by microangiopathic haemolysis, thrombocytopenia, and neurological abnomalities

Aetiology

• Due to a deficiency of metalloproteinase ADAMTS13
  • Can be a hereditary congenital mutation or due to autoimmune inhibition
• Associated with triggers such as medication, AIDS and malignancy

Clinical presentation

Classic pentad:

• Fever
• Microangiopathic haemolytic anaemia (MAHA)
• Thrombocytopaenic purpura
• CNS involvement: headache, confusion, seizures
• AKI

Investigations

• Bloods:
  • FBC: normocytic anaemia (secondary to haemolysis), thrombocytopenia, and possibly a raised neutrophil count
  • U&E: raised urea and creatinine
  • Blood film: schistocytes (consistent with haemolysis), reticulocyte count is elevated
  • Other bloods: LFT, LDH, D-dimer, indirect bilirubin elevated, haptoglobins low
  • Important to differentiate between TTP and DIC - coagulation screen will be normal in TTP, whereas it will be prolonged in DIC with low plasma fibrinogen
  • ADAMST13 assay: low ADAMST13 activity is diagnostic
• Urinalysis: proteinuria and microscopic haematuria

Management

• Fresh frozen plasma (FFP) - contains vWF-cleaving protease and complement components
• Plasma exchange - removes antibodies and toxins associated with the pathogenesis of the disease
• High-dose steroids, low-dose aspirin and rituximab can also be given
• Splenectomy may be used to treat patients who do not respond to plasma exchange, or who relapse chronically