Traumatic haemolysis
- Lesion
Red cells can be cut by abnormal valves, fibrin strands in small vessels or repeated blows to the feet. The fragments show on the smear.
What it is
Mechanical injury destroys red cells inside vessels. Prosthetic heart valves, especially mechanical ones, and severely damaged native valves shear cells by turbulence. Microangiopathic haemolytic anaemia arises when small vessels are narrowed by fibrin or platelet thrombi or damaged endothelium, as in DIC, TTP, HUS, malignant hypertension, lupus, HELLP syndrome and disseminated cancer. Repetitive physical impact, such as long marches or running and drumming, can rupture cells in the feet or hands. All produce fragmented red cells (schistocytes).
Step by step
- The vessel lumen narrows by thrombi or damaged endothelium, or flow becomes turbulent across a valve.
- Red cells are forced through fibrin meshes or high shear zones.
- Cells are cut: fragments and helmet shapes; some lyse at once.
- Haemoglobin is released into plasma and urine.
- Ongoing destruction exceeds marrow compensation in severe cases.
Causes of traumatic haemolysis
| Cause | How cells are injured | Associated features |
|---|---|---|
| Mechanical heart valve or severe valve disease | Turbulence and shear stress | Murmur, iron loss in urine |
| Thrombotic thrombocytopenic purpura | Platelet-rich microthrombi | Thrombocytopenia, neurologic signs |
| Disseminated intravascular coagulation | Fibrin microthrombi | Bleeding, prolonged clotting tests |
| HELLP syndrome and preeclampsia | Endothelial damage and microthrombi | Pregnancy, liver enzymes high, low platelets |
| March haemoglobinuria | Repeated blows to the soles | Transient dark urine after prolonged impact exercise |
Clinical notes
- New anaemia with schistocytes after a valve replacement suggests a paravalvular leak.
- Schistocytes with low platelets require urgent evaluation for TTP.
Test yourself
Think of the answer, then tap the question to see it.
Which red cell forms indicate microangiopathic haemolysis?
Schistocytes: fragments, helmet cells and triangle cells.
Which kind of prosthetic valve causes more haemolysis?
Mechanical valves, more than bioprosthetic (animal tissue) valves.
What are four causes of microangiopathic haemolytic anaemia?
DIC, TTP, HUS and malignant hypertension (also HELLP syndrome, lupus and disseminated cancer).
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Hemolytic anemia: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Thrombotic thrombocytopenic purpura: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).
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Representative model, for educational purposes only.