A platelet count is a test to measure how many platelets you have in your blood. Frequently referred to as thrombocytes, platelets are a type of blood cell that helps the blood to clot. Along with red blood cells and white blood cells, platelet levels are assessed with a comprehensive blood count (CBC). Specifically, the platelet evaluation includes: platelet count, mean platelet volume, and platelet distribution width. Most people have a CBC performed as a part of a routine health examination. A CBC may also be ordered when a person has signs and symptoms that may indicate a disorder involving blood cells, such as:
- Fatigue, weakness
In addition, when a person is diagnosed with a disease known to affect blood cells a healthcare professional will order routine CBCs to monitor the condition. Similarly, if someone is receiving treatment for a blood-related disorder, then a CBC will be ordered routinely to determine the efficacy of the treatment. Further, when someone is taking medications known to affect bone marrow production of cells or decrease white blood cell count overall (e.g., chemotherapy), routine CBC can be used to monitor the treatment.
A low platelet count is known as thrombocytopenia. Thrombocytopenia can occur as a result of a separate disorder, such as leukemia or an immune system problem. Or it can be a side effect of taking certain medications.
Thrombocytopenia may be mild and cause few signs or symptoms. In rare cases, the number of platelets may be so low that dangerous internal bleeding occurs. Treatment options are available.
Thrombocytopenia signs and symptoms may include:
Easy or excessive bruising (purpura):
Purpura, also called blood spots or skin hemorrhages, refers to purple-colored spots that are most recognizable on the skin. The spots may also appear on organs or mucous membranes, including the membranes on the inside of the mouth.
Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on the lower legs. Petechiae are tiny purple, red, or brown spots on the skin. They usually appear on your arms, legs, stomach, and buttocks. You might also find them inside your mouth or on your eyelids.
Prolonged bleeding from cuts
Bleeding from your gums or nose
Blood in urine or stools
Unusually heavy menstrual flows
In jaundice, the skin and whites of the eyes look yellow. Jaundice occurs when there is too much bilirubin (a yellow pigment) in the blood—a condition called hyperbilirubinemia.
Thrombocytopenia can be inherited or it may be caused by a number of medications or conditions. Whatever the cause, circulating platelets are reduced by one or more of the following processes:
1. Trapped platelets
The spleen is a small organ about the size of your fist located just below your rib cage on the left side of your abdomen. Normally, your spleen works to fight infection and filter unwanted material from your blood. An enlarged spleen — which can be caused by a number of disorders — may harbor too many platelets, causing a decrease in the number of platelets in circulation.
2. Decreased production of platelets
Platelets are produced in your bone marrow. If production is low, you may develop thrombocytopenia. Factors that can decrease platelet production include:
- Some types of anemia
- Viral infections, such as hepatitis C or HIV
- Chemotherapy drugs
- Heavy alcohol consumption
3. Increased breakdown of platelets
Some conditions can cause your body to use up or destroy platelets more rapidly than they’re produced. This leads to a shortage of platelets in your bloodstream. Examples of such conditions include:
- Pregnancy. Thrombocytopenia caused by pregnancy is usually mild and improves soon after childbirth.
- Immune thrombocytopenia. This type is caused by autoimmune diseases, such as lupus and rheumatoid arthritis. The body’s immune system mistakenly attacks and destroys platelets. If the exact cause of this condition isn’t known, it’s called idiopathic thrombocytopenic purpura. This type more often affects children.
- Bacteria in the blood. Severe bacterial infections involving the blood (bacteremia) may lead to destruction of platelets.
- Thrombotic thrombocytopenic purpura. This is a rare condition that occurs when small blood clots suddenly form throughout your body, using up large numbers of platelets.
- Hemolytic uremic syndrome. This rare disorder causes a sharp drop in platelets, destruction of red blood cells and impairment of kidney function. Sometimes it can occur in association with a bacterial Escherichia coli (E. coli) infection, such as may be acquired from eating raw or undercooked meat.
- Medications. Certain medications can reduce the number of platelets in your blood. Sometimes a drug confuses the immune system and causes it to destroy platelets. Examples include heparin, quinine, sulfa-containing antibiotics and anticonvulsants.
Dangerous internal bleeding can occur when your platelet count falls below 10,000 platelets per microliter. Though rare, severe thrombocytopenia can cause bleeding into the brain, which can be fatal.
When to see a doctor
Make an appointment with your doctor if you have any warning signs that worry you. Bleeding that won’t stop is a medical emergency. Seek immediate help if you experience bleeding that can’t be controlled by the usual first-aid techniques, such as applying pressure to the area.
A high platelet count, known as thrombocytosis, can be caused by:
- Cancers (lung, breast ovarian, gastrointestinal)
- Inflammatory disorders like lupus and rheumatoid arthritis
- Iron deficiency anemia
- Hemolytic anemia
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