Thrombotic microangiopathies

Abstract

Thrombotic microangiopathies (TMAs) are a group of rare diseases characterised by microangiopathic haemolytic anaemia, thrombocytopenia and occlusion of small vessels by thrombi; the site and severity of which determine the clinical presentation. A diagnosis of TMA should be considered in any patient presenting with a combination of haemolytic anaemia and thrombocytopenia as TMA can rapidly progress to organ failure and death. The two main TMAs, haemolytic uraemia syndrome (HUS) and thrombotic thrombocytopenia purpura (TTP), were previously defined according to their clinical manifestations. HUS typically causes kidney injury, whereas in TTP neurological involvement predominates. Although in many cases the diagnosis is clear, in other cases it is not possible to reliably distinguish between these diseases purely on clinical criteria, particularly with HUS in which neurological involvement is a frequent finding. In addition, other organ involvement can also occur, further complicating the diagnosis. As a better understanding of the molecular basis of HUS and TTP develops, it is now possible to diagnose and differentiate between these diseases with greater accuracy. However, recognition of a TMA by clinicians is essential for the timely diagnosis and treatment of TMA.