Biology Question #3423

Chanell, a 17 year old female from South Africa asks on April 29, 2006,

Why do some people bruise more easily than others? What is it that makes some people more sensitive to physical contact than others?

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The answer

David Winsemius answered on May 10, 2006

The quick answer: if this is a problem for you or someone close to you, go see your doctor. We cannot give medical advice over the Internet.

Bruising occurs when blood gets released from blood vessels and becomes a stain under the skin. Associated with such a release is the process of blood clotting, or the thickening of the blood so that it does not flow forever. There are very complex ways that the body uses to promote clotting at the site of an injury but the body must also prevent clotting when the blood should be flowing. A blood component responsible for clotting called platelets will clump at the site of injury and release other signalling proteins and chemicals. There is a protein in the blood called fibrinogen that gets converted to a sort of glue-protein called fibrin by enzymes called clotting factors. There are also proteins called fibrinolytics that break up clots so the body can finish healing. The lining of the blood vessels helps regulate this delicate balance. The whole system needs to be ready to work at a moments notice but it also needs to not work when it is not needed.

Some people develop bruises much more easily than average. That is not necessarily a disease, but could rather be a variation within the population. If someone is bothered by easy bruisability, their doctor will probably:
-- do an examination of the skin,
-- take a good family history,
-- get a list of all medications and herbal remedies being taken
-- and do some basic blood tests: a "blood count" and what is sometimes called a "blood profile" or a "multiphasic panel".

That last one is a group of 12 to 20 lab tests of sugar metabolism, kidney function, liver function and some test of bone activity. If the person has had any in bleeding into the joints or serious nosebleeds then they would probably get further tests of clotting function. If there has been any clotting problems, then a different set of tests would be done.

The first tests of clotting function would be the prothrombin time (called "PT" by doctors) and activated partial thromboplastin time (usually shortened to "aPTT").

There is a very long list of disease conditions that can cause easy bruising. These are only some of them. You can see why giving one answer would be impossible and why a doctor needs to be consulted:

Medications that interfere with platelet function such as aspirin, the non-steroidal anti-inflammatories, Vitamin deficiencies such as vitamin K and vitamin C, Vitamin K deficiency can be caused by intestinal disorders or malabsorbtion. Both vitamin K and vitamin C defiencies can be caused by inadequate diet. Platelet or clotting deficiencies, the most common of which is von Willeband's disease, as well as idiopathic thrombocytopenic purpura, factor VIII deficiency (Hemophilia A), factor IX deficiency (Hemophilia B), and alpha2-plasmin inhibitor deficiency. Collagen disorders such as Ehlers-Danlos syndrome, Marfan syndrome, Cutis Laxa (Elastolysis), and hereditary hemorrhagic telangiectasia. Excessive or prolonged use of corticosteroids such as prednisone. Severe liver disease (since the liver makes many of the clotting factors.) Bone marrow disorders and leukemia (since platelets are produced in the bone marrow). Chronic Kidney Disease, etc.

Further information can be found at the Merck Manual and eMedicine:

Hemostasis And Coagulation Disorders, Platelet Disorders, Vascular Bleeding Disorders, Inherited Connective Tissue Disorders, Vitamin C deficiency, eMedicine's Hematology sections

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