Pathology > Basic Hematology > Red Cell Disorders > Mechanical Trauma

Mechanical Trauma

RBC fragmentation may be caused by RBCs striking against abnormal surfaces (aortic stenosis; atherosclerosis) or artificial surfaces (prosthetic heart valves; arterial grafts).

Schistocytes secondary to mechanical trauma.

Microangiopathic hemolytic anemia is caused by RBCs torn apart on fibrin strands strung across small vessels or on damaged endothelial surfaces of small vessels (akin to a road under construction causing damage to your car). This accompanies disseminated intravascular coagulation (DIC), malignant hypertension, hemolytic uremic syndrome (HUS), thrombotic thrombocytopenia purpura (TTP), pre-eclampsia, and some vascular neoplasms.

The numerous RBC fragments are a result of TTP.

Thrombotic thrombocytopenia purpura (TTP) is caused by fibrin and platelet deposition in small vessels fragmenting RBCs as they flow past.

Patients with TTP are usually adults with neurologic and mild renal abnormalities. There may be fever.

Schistocytes and severe thrombocytopenia are classic. PT and PTT studies are normal

Hemolytic uremic syndrome (HUS) is similar to TTP, but is more common in children and involves primarily the kidney. Neurologic abnormalities are absent.

Fibrin and platelet deposition are primarily seen in the microvasculature of the kidney.

Schistocytes and severe thrombocytopenia are classic. Again PT and PTT studies are normal.

The prognosis of HUS is better than TTP.

HUS is associated with infection, especially E. coli which produces verocytotoxin.

Fibrin-platelet thrombi in glomerular and interstitial vessels. Masson- trichrome staining fibrin red.

Slide thanks to Dr. Kline Bolton, UVA.

"Joggers" or "march" hemoglobinuria results from trauma to red cells occuring in the feet, usually secondary to jogging, running, or marching. No RBC changes are seen on the PBS.

Beginning with the next card we will look at several "miscellaneous" difficult to classify causes of hemolysis.

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