Hemolytic Uremic Syndrome and TTP

Hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are rare but serious conditions in which tiny blood clots form in small blood vessels, damaging red blood cells and organs such as the kidneys and brain. Both are forms of thrombotic microangiopathy (TMA) and need urgent hospital care. A nephrologist works with haematologists and critical care teams to manage these conditions.

What Are HUS and TTP?

In thrombotic microangiopathy, the lining of small blood vessels is injured and small clots form. Red blood cells break as they pass through these vessels (haemolysis), platelets are used up, and organs receive less blood.

HUS mainly affects the kidneys and can cause acute kidney injury. TTP more often affects the brain, though the kidneys may also be involved. Distinguishing between them is important because treatment differs.

Causes and Types

Several different processes can lead to these conditions.

Although these conditions are uncommon, they can progress rapidly, and early specialist care makes a meaningful difference. Because the symptoms may look like those of other illnesses, such as gastroenteritis, severe infection or pregnancy complications, doctors rely on a combination of blood tests to recognise them quickly and begin appropriate treatment.

• Infection-related HUS, often following diarrhoea caused by certain strains of E. coli, more common in children
• Atypical HUS, linked to abnormalities in the complement system of the immune system, which may be inherited
• TTP, caused by severe deficiency of an enzyme called ADAMTS13, usually due to autoantibodies
• Secondary causes such as pregnancy and the postpartum period, certain medicines, cancer, autoimmune disease, severe hypertension and infections

Symptoms

Symptoms can develop quickly and require urgent medical attention.

• Diarrhoea, sometimes bloody, preceding infection-related HUS
• Pale skin, tiredness and breathlessness from anaemia
• Small red or purple spots on the skin, or easy bruising
• Reduced urine output, swelling or high blood pressure
• Yellowish discoloration of the skin or eyes
• Confusion, headache, seizures or weakness, particularly in TTP

Diagnosis

Doctors look for a combination of low platelets, anaemia due to broken red cells and organ damage. Tests may include a complete blood count, a peripheral blood smear to look for fragmented red cells, LDH, bilirubin, haptoglobin, kidney function tests, stool tests for infection, ADAMTS13 activity and complement studies. A kidney biopsy may be performed in selected cases once it is safe to do so.

Treatment

Treatment is given in hospital and depends on the type. It is coordinated between the nephrologist, haematologist and other specialists.

• Supportive care with fluids, blood pressure control and careful blood transfusion when needed
• Plasma exchange, particularly for TTP, often started urgently
• Immune-suppressing treatment for autoimmune TTP, as directed by the haematology team
• Complement-inhibiting therapy for atypical HUS in suitable patients
• Treating or removing secondary triggers such as a responsible medicine
• Dialysis support if kidney function is severely affected
• Long-term follow-up of kidney function and blood pressure

When to See a Nephrologist

HUS and TTP are medical emergencies, so anyone with the warning signs above should go to hospital immediately. After recovery, regular nephrology follow-up is important because some people may have lasting kidney damage, high blood pressure or a risk of relapse, particularly with atypical HUS.

This page is for general information only and is not a substitute for a medical consultation. Please consult a qualified doctor for diagnosis and treatment.