Bruises are not a pleasant sight, and it’s easy to feel discomfort or concern if your notice a dark or bluish patch in your arms or legs, especially if you don’t recall any trauma in that particular site.
What are bruises and how do they form?
Skin is very vascular. This organ which is the largest in our body with a surface area of more than 2 and a half square meters has to be supplied by a complex network of blood vessels called capillaries. They serve to deliver oxygen and nutrition uniformly to our skin cells. This is the reason why white-skinned individuals especially from Nordic countries have a pinkish tinge to their skin. It can also serve to assess the perfusion of the skin if such tinge is replaced with a pale white color and sometimes, to assess the oxygenation of the blood if such pinkish tinge turns bluish.
Bruises form when blood capillaries are injured, and blood is released into the skin layers. This is not uncommon and the skin -being the interface of our body into the surrounding environment- is very liable to trauma, but the ease of such injury to cause bleeding and the amount of blood released before our hemostatic mechanisms -those which form a blood clot to stop the bleeding- kick in differ according to the individual and the integrity of the hemostatic system.
The bruise has different colors depending on its age and the skin color of the person. People with a lighter skin tone tend to have bruises which are bluish or purplish while those with a darker skin tone have dark purple, brownish or even black bruises. The bruise ages with a change of color due to the change of hemoglobin found in red blood cells released from the ruptured capillaries. On the first 2 days, the bruise is reddish with edema from the release of inflammatory mediators and with the normal color of red cells. Two to five days later, the color becomes bluish with the loss of oxygen that the red cell carries and its attachment to carbon dioxide which causes the hemoglobin to become bluish. A week after the injury, the color becomes greenish due to the conversion of hemoglobin into biliverdin, which is green in color. Biliverdin is then converted to bilirubin -the chemical substance which if released in excess can cause jaundice in some diseases-. Afterwards, the bruise becomes dark brown and slowly begins to disappear.
Are all spots on the skin bruises?
It is a common misconception that any bluish patch or spot on the skin is a “bruise”. While bruises form the majority of spots that appear as bluish, reddish or brownish on the skin of the arms and legs, a common differential diagnosis that is usually considered by physicians is a “rash”. Rash is a general term and can include different shapes and sites of appearance. The rash of herpes, for example, is very different than that of allergy and that of bacterial infections differs from that of scabies. The rash that looks like bruises is called a hemorrhagic rash. It can result from infections including:
- Coxsackievirus A19, which mostly causes mild illnesses
- Echovirus, which can cause a multitude of infections from mild fever-like illnesses to severe infections including meningitis -infection of the coverings of the brain- and endocarditis -infection of the inner lining of the heart and heart valves-.
- Cytomegalovirus, which mostly affects the liver, lymph nodes and the spleen.
- Meningococcemia, which is meningitis caused by Neisseria gonorrhea bacteria. It is a life-threatening infection.
- Bacterial endocarditis can also cause a hemorrhagic rash
Another common differential diagnosis of bruises is what we call a vasculitis rash. Blood vessels can be inflamed in multiple conditions and a rash develops if this inflammation involves the small blood vessels close to the skin. This condition is termed small vessels vasculitis, and the rash resulting from such condition has the special character of being raised above the skin unlike other rashes which are normally on the same level of the skin. Causes of vasculitis rash include:
- Henoch-Schönlein purpura: Which is a type of immune-mediated vasculitis that occurs in infants and young children.
- Urticarial vasculitis: Which is an exaggerated form of an allergic condition.
- Exercise induced vasculitis: Which is a harmless condition affecting females aged 50 years old or more following intense physical exercise.
- Cutaneous polyarteritis nodosa: Which is an immune mediated inflammation of the small and medium-sized blood vessels and usually follow an infection by hepatitis viruses or HIV.
Are bruises dangerous?
Bruises in themselves are not dangerous. They are actually a physiological response of a well-perfused skin and an effective hemostatic blood clotting mechanism. In fact, dead people do not bruise, and the last bruise can be used to determine the time of death -along with other 100 or so forensic signs-, therefore the mere presence of bruises should not call for concern. The cause of bruising, however, can be dangerous or life-threatening either due to excessive bleeding elsewhere in the body or because of other systems or organs that the disease hits. Easy bleeding or bruising can be caused by the following:
1) Defects in platelets:
Our platelets are the first line of defence against us “bleeding until death”. When you injure a blood vessel, the smooth lining covering its inner surface becomes rough and platelets recognize that. The small cellular fragments stick to the exposed part and to themselves forming a “plug” that enlarges in size until it fills as much of the defect as possible to prevent further leakage.
Platelets are formed in the bone marrow from large mother cells called megakaryocytes. They then exit from the bone marrow and circulate for an average of 7 days before being disposed of and replaced. Normal platelet count in a healthy individual is 150,000-450,000 per cubic microliter.
- Low platelet count: If platelet count drops below 150,000 per cubic microliter, controlling even minor leakage from blood vessels becomes difficult. Furthermore, if the platelet count drops beyond 50,000 per microliter, the incidence of life-threatening hemorrhage becomes high especially into the brain.
- Abnormal platelets: In order for platelets to carry out their function properly, they need proper adhesion to the surface and aggregation over one another. In some cases, and due to drugs or inherited abnormalities, this is lost. So, even though platelet count is normal, platelets may still have difficulties performing their normal functions. The collective term for such a disorder is thrombasthenia.
2) Coagulation problems:
Blood coagulation refers to the ability of the blood to form a blood clot. The process is by no means simple and many mechanisms share in its formation. After the first platelet identifies the defective vessel wall, the coagulation cascade starts through the activation of many proteins called coagulation factors and the end product is the conversion of an inactive protein called fibrinogen to its active form “fibrin”. Fibrin then aggregates in the form of threads or fibers in between the aggregated platelets to form the blood clot. Defects in the coagulation pathway will result in easy bruising, but if isolated with no defects in platelets, it is highly unlikely that they will cause spontaneous bleeding. The most common defects in the coagulation pathway include:
- Hemophilia: hemophila is divided into 2 main types, A and B depending on the defective coagulation factor. Hemophilia A results from a defective factor VIII. This defect is inherited as a sex-related trait, which means that males are much more likely to be affected since they have only one copy of the X chromosome while females have 2 copies and if one of them doesn’t have a defective gene, the female won’t manifest any of the symptoms, but will carry it on to her sons. Hemophilia B is similar to hemophilia B but here, the defective factor is factor IX. In both cases, patients experience easy bruising and excessive bleeding following injury and can even become disabled due to repetitive bleeding into joints especially the knee joint.
- Von Willebrand factor deficiency: Von Willebrand factor is a protein that helps bind platelets to the vessel wall and initiate platelet adhesion and aggregation. It also helps start the coagulation pathway. Defective Von Willebrand factor will show manifestations of defective platelets and defective coagulation.
3) Liver disease:
The liver is responsible for the formation of most proteins in our circulation including albumin, which forms the bulk of proteins in our blood and most coagulation factors. The liver can lose its function due to chronic or acute causes. Diseases like hepatitis whether acute or chronic, viral or autoimmune as well as alcoholic and non-alcoholic fatty liver can damage the liver beyond its capacity to produce enough prothrombin, a key protein and enzyme in coagulation. This can cause easy bruising along with other manifestations of liver disease like jaundice, malnutrition, ascites, gastrointestinal bleeding and hepatic encephalopathy -central nervous system derangement in hepatic failure-.
4) Kidney disease:
The kidney produces 2 important hematological proteins called erythropoietin and thrombopoietin. They serve to stimulate the bone marrow to produce more red cells and platelets, respectively. In chronic kidney disease, the levels of both fall causing a fall in platelet count and easy bruising as well as spontaneous bleeding.
Another cause of easy bleeding and bruising in chronic kidney disease is the accumulation of urea, a by-product of protein metabolism in the body. Urea is mainly excreted by the kidney in healthy individuals and a fall in renal functions causes its levels to rise and toxicity to manifest. Urea increases bleeding time through many mechanisms and many of those are theoretical, but it is believed that the main one involves impairing the ability of platelets to stick to vessel walls.
5) Cushing syndrome:
Cushing syndrome is a disease that occurs when your body is exposed to high level of steroids whether from outside the body as in the form of supplements or drugs for medical conditions like asthma, or from inside as a result of excessive secretion or tumors. People with Cushing experience stretch marks and easy bruising. The reason for easy bruising isn’t as direct as the above causes and is mainly thought to be a result of the rapid stretching of the skin due to the rapid weight gain of such patients especially in the trunk area owing to the accumulation of water and salts. This renders the connective tissue supporting the blood vessels weak and thin, causing easy tearing of such blood vessels especially at the sites of stretch marks causing the characteristic purplish stretch marks termed “stria rubra”.
6) Cancer:
When dealing with cancer, people usually have the general conception that cancers are infinitely growing tumors that eventually “eat up” the body from the inside, and despite the fact that this isn’t so far-fetched as regarding solid tumors, the situation is very different in blood cancers. Blood cancers are called leukemias and the common character that defines them is the proliferation of one or more “lines” of cells that eventually invade the bone marrow, lymph nodes, the liver, the spleen and other structures impairing their function. Sometimes, it is not the cancer itself but the agents used in its treatment that cause coagulation problems or aggravate existing ones. For example, radiotherapy commonly used in blood cancers and testicular cancer can damage the bone marrow causing a drop in platelet count and increasing the risk of bleeding or easy bruising.
7) Drugs:
Many drugs can cause bruising and it is considered one of the most common causes of easy bruising and spontaneous bleeding. Drugs can cause bruising as an exaggeration of its normal desired effect such as Aspirin is an antiplatelet drug that helps prevent the formation of blood clots in hypertensive patients and those with recurrent blood clots. It normally increases bleeding time, but in some cases, it can cause prolonged bleeding beyond the desired effect.
Another class of drugs with a similar action is anticoagulants. These drugs act on the coagulation cascade mostly through the inhibition of single or multiple coagulation factors. The most commonly used of these drugs are Heparin and Warfarin. Heparin is taken as an injection and warfarin as tablets. They rarely cause spontaneous bleeding unless taken in great excess but can cause easy bruising. Both of these drugs are monitored by special tests to assess the degree of anticoagulation achieved and to make sure that it never exceeds or falls below the desired value.
On leukemia and bruising
Leukemia is divided into acute and chronic types, and symptoms can vary widely between types, however a very common symptom that may even precede diagnosis is easy bruising. It is easy to confuse leukemia bruising with those occurring due to other conditions or even those resulting from trauma. In anxious individuals, this can cause unnecessary concern. Some key points as to how to differentiate between bruises due to benign causes and those when a malignant condition is suspected are the following:
- Bruises of leukemia tend to occur at sites unlikely exposed to trauma. If bruises develop on the trunk, head or neck for example, it could point towards a serious condition.
- Their multiplicity
- Their unexplained appearance with no memory of a trauma
- Their association with bleeding
- Their association with other symptoms of leukemia such as fatigue, night sweating, unexplained loss of weight and frequent infections.
As mentioned above, the reason as to why excessive bleeding develops in leukemia can either be attributed to a deficiency of platelets in acute leukemia due to the destruction of their mother cells or their replacement by malignant cells, or the presence of excess yet dysfunctional platelets in chronic leukemia.
Besides bruising, leukemia patients may complain of what looks like a rash. This is called petechiae, and they are small sites of bleeding into the skin that occur when a small blood vessel supplying the skin ruptures, and due to the deficiency of platelets, the defect in the blood vessel takes a long time to be clogged producing the characteristic small sport of bleeding into the skin. If those spots are grouped together, they produce a rash-like appearance.
Leukemia is a complex disease, and the combination of symptoms that it produces can vary according to the type, severity and person it affects. If you notice any of the danger signs mentioned above, it would be wise to seek medical care, otherwise, don’t be overanxious about every bruise.