Thrombotic microangiopathy (TMA) is a rare but potentially life threatening condition that affects the body’s small blood vessels. TMA occurs in about 1 to 3 people out of 1 million.

TMA can be hereditary, but it can also develop due to the body’s response to pregnancy, certain serious illnesses, or medications.

While the condition is often treatable, the outlook for someone with TMA depends largely on the underlying cause of the disease.

This article will take a closer look at TMA, its causes, symptoms, treatment, and prognosis.

The term “thrombotic” refers to a blood clot. And “microangiopathy” is a medical situation affecting small blood vessels — specifically capillaries and arterioles. So TMA is a condition in which blood clots have formed in those blood vessels.

However, TMA also causes a reduction in circulating platelets because the blood clots are made of platelet clumps. The associated destruction of red blood cells is called hemolytic anemia.

While small blood vessels anywhere in the body may be affected, the kidneys and the brain are among the organs most likely to experience TMA, which can lead to problems with organ function.

There are several types of TMA. Two of the more common versions are thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS).

Thrombocytopenic purpura (TTP)

TTP occurs when there is low activity of the protein ADAMTS13. This protein is involved in the regulation of blood clotting.

In some cases, a person is born with a mutation in the gene ADAMTS13. Other people with TTP develop a type of autoimmune disorder that interferes with the activity of the ADAMTS13 gene.

Hemolytic uremic syndrome (HUS)

HUS often develops after a serious bowel infection, typically caused by the bacteria E. coli. This type of TMA primarily affects the small blood vessels of the kidneys.

Symptoms of TMA depend primarily on the part of the body affected by the disease. For example, with low platelet counts, a person may be more likely to bruise and have bleeding problems.

When low red blood cell counts develop, symptoms can include:

When the kidneys are involved, a person can have abnormal kidney function. Symptoms could possibly include high blood pressure. They may also have a fever especially if they’re diagnosed with TTP.

When blood vessels in the brain are affected, symptoms can include:

A person with TMA may have a primary form of the disease, which means it developed on its own and not as a complication from another cause.

When there’s an underlying cause that triggers TMA, it’s considered a secondary form of the disease. A majority of TMA cases represent secondary TMA.

Some of the more common causes of thrombotic microangiopathy include:


In a 2019 study involving more than 500 individuals with TMA, researchers determined that 35 percent of the cases were associated with pregnancy. According to research, pregnancy-related TMA is usually characterized by:

  • a breakdown of red blood cells (hemolysis)
  • elevated liver enzymes
  • low platelet count syndrome


Both viral and bacterial infections can lead to TMA complications. Viral infections can include:

An E. coli infection remains the most common bacterial infection known to cause TMA.


A review of more than 600 TMA studies suggests that the mechanism behind drug-induced TMA isn’t well understood. However, there are several drugs particularly associated with the disease. These include:


Cancer-related TMA may develop from a cancer itself or from treatment — particularly chemotherapy drugs, such as mitomycin C.

A 2016 review of research suggests that TMA originating from cancer treatment drugs may be more serious and that the prognosis is more encouraging when TMA develops as a result of the underlying cancer.

Malignant hypertension, which is sudden, abnormally high blood pressure, is also a known contributor to TMA.

Other causes include:

The right treatment for TMA depends on the nature of the disease. TTP, for example, is often treated with a plasma exchange. This involves the removal of plasma — water, salts, and enzymes — from the blood. You’ll then receive fresh donor plasma to replace what was removed.

With hemolytic uremic syndrome (HUS), intravenous fluids and nutritional supplements may be sufficient. Blood transfusions may be necessary to reduce symptoms and prevent future complications.

If kidney damage is severe, dialysis may be necessary on a temporary basis to maintain kidney function and help resolve TMA.

Other treatments are dictated by the cause of the TMA. If a bacterial infection is detected, antibiotics may be prescribed. An autoimmune disorder may require the use of immune suppression therapies.

The survival rates for TMA vary considerably, given that they’re associated with so many different possible causes and can take on several different forms.

A 2021 study involving 239 people suggests that the overall mortality rate during the 11-year follow-up period was 23 percent.

However, it should be noted that TMA cases triggered by cancer and other malignancies are more likely to have a poorer outlook than those diagnosed during pregnancy, for example.

The outlook for TTP depends greatly on whether you undergo treatment.

The Thrombotic Thrombocytopenic Purpura Foundation suggests that without treatment, 95 percent of individuals with TTP may die from the disease. With treatment, up to 90 percent of people can achieve remission, though nearly one-third may relapse.

The National Kidney Foundation reports that about 85 percent of common HUS cases resolve completely. However, if there was significant kidney damage, some kidney problems and high blood pressure may be more likely later on.

Thrombotic microangiopathy (TMA) is a rare but serious disease characterized by blood clots in the body’s smallest blood vessels, especially the kidneys and brain. TMA is usually a complication stemming from another health condition or pregnancy.

Treatment for TMA may include blood transfusions, plasma exchange, and other treatments.

By getting a proper diagnosis and prompt treatment, this uncommon blood disorder is often treatable. Ongoing monitoring after treatment is usually necessary; it’s an important step in keeping TMA from returning and causing further problems.