Thrombocytopenia is an abnormal drop in the number of blood cells involved in forming blood clots
. These cells are called platelets.
Thrombocytopenia is a blood disease characterized by an abnormally low number of platelets in the bloodstream. The normal amount of platelets is usually between 150,000 and 450,000 cells per microliter of blood. A microliter is an amount equal to one one-millionth of a liter (a liter is almost equal to a quart). Platelet numbers are counted by having a blood sample collected and placing a measured amount of blood in a machine called a cell counter. When the platelet number drops below 150,000 cells per microliter of blood, this person is said to be thrombocytopenic.
Causes and symptoms
Abnormal reductions in the number of platelets are caused when abnormalities occur in any of the following three processes: decreased platelet production by the bone marrow; increased trapping of platelets by the spleen; or a more rapid than normal destruction of platelets. Persons with this condition easily bruise and can have episodes of excess bleeding (a hemorrhage).
Platelets come from megakaryocytes, which are produced in the material located within the center cavity of the bones (bone marrow). When abnormalities develop in the marrow, the marrow cells can lose their ability to produce platelets in correct amounts. The result is a lower than normal level of platelets in the blood. Drugs used in cancer chemotherapy can cause the marrow to malfunction in this way, as can the presence of tumor cells in the marrow itself.
Normally, the spleen holds about one-third of the body's platelets as part of this organ's function to recycle aging
or damaged red blood cells (the cells that carry oxygen in the blood). When liver disease
or cancer of the spleen is present, the spleen can enlarge, resulting in a greater number of platelets staying in the organ. This condition results in abnormally low numbers of platelets in the blood.
Platelets can break down in unusually high amounts in persons with abnormalities in their blood vessel walls; with blood clots; or with man-made replacement heart valves. Devices placed inside blood vessels to keep them from closing (stents) due to weakened walls or fat build-up can also cause platelets to break down. In addition, infections and other changes in the immune system can speed up the removal of platelets from the circulation.
Thrombocytopenia is diagnosed by having a blood sample taken and counting the platelets present in the sample. However, accurately determining the medical reason for this conditions is complex.
Once a low platelet count
is verified, a careful evaluation of the function of the bone marrow and spleen are necessary. Improper functioning of either or both of these organs can cause thrombocytopenia. In addition, the causes for the abnormal spleen or marrow function must be investigated since different cancers, blood disorders, or liver disease can be the true cause for the drop in platelets found in the blood.
If low platelet counts are caused by an enlarged spleen, removal of the spleen can help raise the platelet level, since the spleen is no longer there to capture the platelets. However, proper treatment for what causes the enlarged spleen is necessary as well.
Low platelet counts can indicate more serious conditions. If a dysfunctional immune system is found to be the cause for this condition, drugs like steroids or gamma globulin can be used to help maintain platelet levels in certain cases.
If low platelet levels are due to an abnormally low level of platelet production, transfusions of platelets can be given as well.
Thrombocytopenia can result in fatal bleeding, but it also can indicate various other, more serious, cancers and disorders that affect the blood cells. This condition requires thorough medical evaluation.
There is no known way to prevent hrombocytopenia.
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.
— One of a group of proteins found in the blood that is involved in helping the body fight infections.
— A man-made surgical device, usually tube-shaped, that is placed into a blood vessel to keep it from closing.
— The transfer of blood from one person to another. Transfusions can be direct, in which blood is transferred from the donor to the recipient; or indirect, in which the blood is taken from the donor, stored in a container, and then given to the recipient.
decrease in number of platelets
in circulating blood; it can result from decreased or defective platelet production or from accelerated platelet destruction. Conditions related to defective production include hypoplastic or aplastic anemia, infiltration of bone marrow by malignant cells or myelofibrosis, viral infections, nutritional deficiency, and thrombocytopenic purpura.
Increased destruction of platelets can be caused by infections, certain drugs, transfusion-related purpuras, idiopathic thrombocytopenic purpura, and disseminated intravascular coagulation. adj., adj
Patient Care. A major concern is prevention of excessive bleeding from trauma to the mucous membranes, skin, and underlying tissues. All injection and puncture sites, whether from intramuscular, subcutaneous, or intravenous administrations or from bone marrow aspiration and other tests, are carefully monitored for signs of bleeding. These procedures should be coordinated and scheduled so that the number of times the skin is broken is kept to an absolute minimum. If, after withdrawal of a needle or catheter, there is evidence that normal clotting is not taking place, pressure is applied immediately and maintained for 10 to 15 minutes.
Because of the potential for trauma to the rectal mucosa, body temperature should not be taken rectally. Blood pressure cuffs, tourniquets for venipuncture, and similar devices must be used with caution. Hence all persons involved with direct patient care should be apprised of the need for special precautions. When used, antiembolic stockings must be thigh-high, never knee-high.
Patients with a chronic deficit of platelets will need instruction in self-care to avoid inadvertent trauma and irritation. For example, to protect the oral mucosa, a soft toothbrush must be used; dental floss, toothpicks, and other items likely to irritate or cause a break in the mucosa should be avoided. Patients are taught to keep their lips and nasal membranes soft and moist, possibly with KY jelly or some other water-soluble lubricant. An oral intake of fluids above the usual maintenance level is encouraged.
To protect the gastrointestinal mucosa, patients are warned to avoid constipation, extremely rough and hard-to-digest foods such as peanuts and popcorn, and aspirin, steroids, and other drugs known to be irritants. Aspirin, in addition to causing gastrointestinal irritation, also interferes with platelet function.
decrease in number of platelets in circulating blood. See also purpura
due to alloantibodies generated in response to blood transfusions or to maternal alloimmunization. Caused by the exposure of the platelets of a newborn animal to platelet alloantibodies which are present in the colostrum of the dam. Occurs in piglets as a syndrome of spontaneous hemorrhage at a few days of age. See also immune-mediated thrombocytopenia (below).
excessive utilization of thrombocytes at hemorrhage sites causes significant reduction in circulating platelets.
that associated with a drug being administered. Some drugs named as causing thrombocytopenia are phenylbutazone, diphenylhydantoin, sulfonamides, digitoxin and phenothiazine tranquilizers.
essential thrombocytopenia idiopathic thrombocytopenia
see immune-mediated thrombocytopenia (below).
a loss of platelets caused by the presence of antiplatelet antibodies which can be demonstrated by the platelet factor-3 (PF-3) release test and immunofluorescence of megakaryocytes. Platelet production may be normal or impaired, also caused by antibodies directed against megakaryocytes. Includes alloimmune, autoimmune and some drug-induced thrombocytopenias.
infectious cyclic thrombocytopenia
recurring cycles of parasitemia and reduced numbers of thombocytes in the peripheral blood are seen in dogs infected with Anaplasmaplatys
. Clinical signs are rarely observed, but coinfection may potentiate clinical disease caused by E. canis
see alloimmune thrombocytopenia (above).
that due to neoplastic invasion of the bone marrow.
a form of nonimmune-mediated platelet destruction caused by exposure of platelets to a damaged or artificial surface.
thrombin stimulates platelet aggregation and reduces circulating numbers.
live-virus vaccines may be associated with a transient, nonimmunogenic aggregation and reduction in numbers of platelets.