ConditionBlood & immune system
Microangiopathic Hemolytic Anemia (MAHA)
Microangiopathic hemolytic anemia (MAHA) is a type of anemia in which red blood cells are physically sheared apart as they pass through small blood vessels damaged or clogged by tiny clots. The broken cells, called schistocytes, are seen on a blood smear. MAHA is a sign of a serious underlying condition, such as thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS), disseminated intravascular coagulation (DIC), HELLP syndrome or severe high blood pressure. It usually comes with low platelets and needs urgent hospital diagnosis.
Also called: MAHA, microangiopathic anemia, fragmentation hemolysis, thrombotic microangiopathy (when with low platelets and organ damage)
At a glance
- What it is
- Destruction of red blood cells by mechanical damage in small vessels.
- Key lab sign
- Schistocytes (fragmented red cells) on the blood smear, with signs of hemolysis.
- Main causes
- TTP, HUS, DIC, HELLP syndrome, malignant hypertension, scleroderma renal crisis, some cancers and drugs.
- Symptoms
- Tiredness, breathlessness, pale or yellow skin, dark urine, bruising, and symptoms of the cause.
- Treatment
- Urgent treatment of the cause; plasma exchange for suspected TTP.
When to get help
Call 911 or go to the ER
- Confusion, severe headache, seizures, weakness or speech problems with bruising, tiny red spots or yellow skin
- Bloody diarrhea followed by reduced urine, swelling or pallor, especially in a child (possible HUS)
- Pregnancy or recent birth with upper belly pain, headache, vision changes or high blood pressure (possible HELLP)
- Widespread bleeding or bruising with fever or severe illness (possible DIC)
See a doctor within a day or two
- New tiredness, breathlessness, pale or yellow skin with tiny red or purple spots on the skin
- Dark, cola-colored urine with tiredness
- Very high blood pressure readings with headache or vision changes
How MAHA happens
Normally, red blood cells squeeze easily through tiny capillaries. In MAHA, the lining of small vessels is damaged, or they are partly blocked by strands of fibrin or platelet clots. As red cells are forced through, they are cut into fragments. These schistocytes are destroyed, causing hemolytic anemia.
When MAHA occurs with low platelets and organ damage (often kidneys or brain), doctors call it thrombotic microangiopathy (TMA). A related but different process, mechanical damage from heart valves or devices, is called macroangiopathic hemolysis.
Causes
| Cause | Key features |
|---|---|
| Thrombotic thrombocytopenic purpura (TTP) | Severe deficiency of the ADAMTS13 enzyme, usually autoimmune; very low platelets; brain symptoms; medical emergency |
| Hemolytic uremic syndrome (HUS) | Usually after Shiga toxin-producing E. coli diarrhea in children; acute kidney injury |
| Atypical HUS | Complement system overactivity; kidney failure; can recur |
| Disseminated intravascular coagulation (DIC) | Sepsis, trauma, cancer or obstetric emergencies; abnormal clotting tests and bleeding |
| HELLP syndrome and severe preeclampsia | Late pregnancy or after birth; high liver enzymes and low platelets |
| Malignant hypertension | Very high blood pressure with organ damage |
| Scleroderma renal crisis | Sudden high blood pressure and kidney failure in systemic sclerosis |
| Cancer | Widespread cancer, especially mucin-producing adenocarcinomas |
| Medicines | Some chemotherapy (gemcitabine, mitomycin), calcineurin inhibitors, quinine, and others |
| Other | Antiphospholipid syndrome, lupus, transplant-associated TMA, HIV |
Symptoms
Symptoms of anemia and hemolysis:
- tiredness and weakness
- breathlessness and a fast heartbeat
- pale skin
- yellowing of the skin or eyes (jaundice)
- dark urine
Symptoms from low platelets:
- easy bruising, tiny red or purple spots (petechiae), nosebleeds or bleeding gums
Symptoms from organ involvement and the underlying cause:
- confusion, headache, stroke-like symptoms or seizures (TTP)
- reduced urine, swelling and high blood pressure (HUS, malignant hypertension)
- bloody diarrhea before HUS
- belly pain, nausea and vomiting
- fever
Diagnosis
Key tests:
- Complete blood count: low hemoglobin; platelets usually low
- Blood smear: schistocytes confirm the fragmentation process
- Hemolysis markers: high LDH, high indirect bilirubin, low haptoglobin, high reticulocyte count
- Direct antiglobulin (Coombs) test: negative, which distinguishes MAHA from autoimmune hemolysis
- Clotting tests: prolonged PT, aPTT and low fibrinogen suggest DIC; usually normal in TTP and HUS
- Kidney function and urinalysis
- ADAMTS13 activity: below 10% confirms TTP
- Stool tests for Shiga toxin-producing E. coli
- Pregnancy test, liver tests and blood pressure
- Complement studies and genetic testing for atypical HUS
Doctors use scoring tools such as the PLASMIC score to estimate the likelihood of TTP while waiting for ADAMTS13 results, because treatment should not be delayed.
Treatment
Treatment depends on the cause and is often started before all results are back:
- Suspected TTP: urgent therapeutic plasma exchange, corticosteroids, caplacizumab and rituximab. Platelet transfusions are generally avoided unless there is life-threatening bleeding.
- STEC-HUS: supportive care, fluids, and dialysis if needed. Antibiotics are usually avoided for E. coli O157 diarrhea in children.
- Atypical HUS: complement inhibitors such as eculizumab or ravulizumab.
- DIC: treat the trigger (such as sepsis), with blood products to control bleeding.
- HELLP and severe preeclampsia: prompt delivery of the baby, with blood pressure control and magnesium sulfate.
- Malignant hypertension and scleroderma renal crisis: careful blood pressure lowering; ACE inhibitors are key in scleroderma renal crisis.
- Drug-induced: stop the drug.
- Supportive: red cell transfusions for severe anemia, and folic acid.
Outlook
The outlook depends on the cause and speed of treatment. Untreated TTP is often fatal, but with plasma exchange and modern drugs, most people survive, though relapses can occur. Most children recover from STEC-HUS, though some have lasting kidney problems. HELLP usually resolves after delivery.
Frequently asked questions
What is microangiopathic hemolytic anemia?
Microangiopathic hemolytic anemia is a type of anemia in which red blood cells are torn apart as they pass through damaged or clot-filled small blood vessels. The fragments, called schistocytes, are seen on a blood smear. It always signals an underlying condition that needs urgent diagnosis.
What causes MAHA?
Causes include TTP, hemolytic uremic syndrome, DIC, HELLP syndrome and severe preeclampsia, malignant hypertension, scleroderma renal crisis, widespread cancer, some medicines, and autoimmune conditions such as antiphospholipid syndrome and lupus.
What are schistocytes?
Schistocytes are fragments of red blood cells, often shaped like helmets or triangles, seen under the microscope. They form when red cells are sheared by damaged small vessels or abnormal clots. Finding them is the key clue to MAHA.
What is the difference between TTP and HUS?
Both cause MAHA, low platelets and organ damage. TTP is caused by a severe lack of the ADAMTS13 enzyme and often affects the brain. HUS usually follows E. coli diarrhea in children and mainly damages the kidneys. Atypical HUS involves the complement system.
Is MAHA an emergency?
Yes, MAHA with low platelets is treated as a medical emergency until the cause is known, because conditions like TTP can be rapidly fatal without treatment. Urgent hospital evaluation and often immediate plasma exchange are needed.
Sources
This guide was written from current patient and clinical guidance, including:
- American Society of Hematology: Thrombotic thrombocytopenic purpura guidelines
- International Society on Thrombosis and Haemostasis: Guidelines for the diagnosis and treatment of TTP
- National Heart, Lung, and Blood Institute: Hemolytic anemia; Thrombotic thrombocytopenic purpura
- CDC: E. coli infection and hemolytic uremic syndrome
- Merck Manual Professional Version: Thrombotic microangiopathies