Thrombotic Microangiopathy (TMA)
Characteristics
Thrombotic microangiopathy (TMA) is a clinical syndrome that is characterized by the destruction of red blood cells (hemolytic anemia), a low number of platelets, and organ damage due to the formation of microscopic blood clots in small blood vessels. While almost all organs can be affected by TMA, it most commonly affects the kidneys and the brain. Under the microscope, the blood of patients with TMA contains injured red blood cells known as schistocytes or fragments.
The 2 primary TMAs consist of thrombotic thrombocytopenic purpura (TTP) and atypical hemolytic uremic syndrome (aHUS), a disorder caused by dysregulation of a part of the immune system known as the complement. Notable causes for TMA include infections (e.g., E. coli infection), the intake of certain medication (e.g., quinine or bevacizumab), connective tissue diseases (e.g., systemic lupus erythematosus, or scleroderma), cancer, pregnancy, or an organ transplantation.
Symptoms
TMA often presents very suddenly and can rapidly result in severe illness. The disease can be associated with a wide range of symptoms. Low levels of red blood cells can lead to fatigue, dizziness, or shortness of breath. In contrast, a low number of blood platelets makes patients prone to bleeding (e.g., nose bleeds, bleeding gums, excessive bleeding from minor cuts, etc.) and bruising.
When blood vessels in the kidney are affected, patients can have a decreased urine volume, swollen legs, and a (very) high blood pressure. Damage to vessels in the brain may lead to confusion, sleepiness, and seizures.
Diagnostic tests
As TMA symptoms often occur very suddenly and rapidly result in severe illness, many patients are hospitalized at the time of their diagnosis. A diagnosis of TMA requires a blood tests to evaluate the number of (red) blood cells and a blood smear to assess the presence of schistocytes. The presence of these two things in the absence of another plausible explanation is sufficient for a presumptive diagnosis of TMA.
In addition to this, a number of tests will be performed to assess whether the patient has organ damage that can be attributed to the TMA. Typical organ damage in TMA patients includes a very high blood pressure (malignant hypertension), kidney injury, abdominal pain, diarrhea, stroke, confusion, heart injury, and eye damage.
Treatments
The treatment for TMA depends on the underlying cause. If TTP is diagnosed, immediate plasma exchange is required. For more details on the treatment of TTP we refer to the separate page on this disease entity.
In contrast to TTP which requires immediate therapy, aHUS usually improves on its own. During hospitalization, patients will be given fluids and when the kidney function declines too much, external blood filtration with dialysis may be required. However, once the bacterial infection causing the aHUS resolves, the symptoms will gradually improve.
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