Thrombocytopenia is a condition in which you have a low blood platelet count. Platelets (thrombocytes) are colorless blood cells that help blood clot. Platelets stop bleeding by clumping and forming plugs in blood vessel injuries.
Thrombocytopenia often occurs 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. It affects both children and adults.
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.
Causes of thrombocytopenia can be divided into three categories:
- Impaired production,
- Increased destruction or consumption, and
- Splenic sequestration.
The main causes in each category are outlined below, although there are other less common causes of low platelet count not mentioned in this article.
- Impaired Production
Low platelet count due to impaired production is generally due to problems with the bone marrow. Usually other blood cells (red and white) are also affected by some of these processes, and their numbers may be abnormal.
Some viral infections can cause low platelet count by affecting the bone marrow, for example,
- varicella (chickenpox),
- hepatitis C,
- Epstein-Barr virus (EBV), and
Aplastic anemia (agranulocytosis) is the terminology for bone marrow failure leading to low platelet count usually associated with anemia (low red cell count) and leukopenia or leucopenia (low white cell count). Common causes of aplastic anemia include:
- Infections (parvovirus, HIV);
- Some medications [chloramphenicol, gold, phenytoin (Dilantin), valproic acid (Depakene, Depakote, Depakote ER, Depacon);
- Radiation; or
- Congenital disorders (Fanconi’s anemia).
Many chemotherapeutic drugs commonly cause bone marrow toxicity and thrombocytopenia.
Other causes of thrombocytopenia due to impaired bone marrow production of platelets include:
- Thiazide mediations;
- Alcohol toxicity from long-term alcohol abuse;
- Leukemias and lymphomas,
- Cancers invading the bone marrow; and
- Vitamin b12 deficiency.
- Increased platelet destruction
Increased platelet destruction can cause thrombocytopenia by immunologic and non-immunologic mechanisms.
Immunologic causes of thrombocytopenia can be caused by:
- Certain medications [sulfonamide antibiotics, carbamazepine (Tegretol,Tegretol XR , Equetro, Carbatrol), digoxin (Lanoxin), quinine (Quinerva, Quinite, QM-260), quinidine (Quinaglute, Quinidex), acetaminophen, and rifampin)],
- Transfusion reactions, and
- Rheumatologic conditions (systemic lupus erythematosus or SLE).
Idiopathic thrombocytopenic purpura (ITP) is an immunologic thrombocytopenia in which the immune system mistakenly attacks the circulating platelets (autoimmune). ITP is typically chronic (long-standing) in adults and acute in children.
Heparin-induced thrombocytopenia (HIT) is an immune destruction of platelets mediated by the use of the blood thinner heparin and its related drugs [low molecular weight heparin, called enoxaparin (Lovenox)].
Non-immunologic platelet consumptive processes include:
- Severe infections or sepsis, irregular blood vessel surface (vasculitis,artificial heart valve), or, rarely, disseminated intravascular coagulation or DIC (a serious complication of overwhelming infections, traumas, burns, or pregnancy).
- Other non-immunologic causes of thrombocytopenia are two other rare, but related, conditions called hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). These may result from some viral illnesses, metastatic cancers, pregnancy, or chemotherapy. Other clinical manifestations of these conditions are hemolytic anemia, kidney failure, confusion, and fever. HUS is generally associated with an infectiousdiarrhea in children caused by escherichia coli bacteria (E. coli O157:H7).
HELLP is an acronym for a syndrome seen in pregnant women that causes hemolytic anemia (blood cells rupture), elevated liver enzymes, and low platelets.
- Splenic sequestration
Splenic sequestration occurs when the spleen enlarges(for example, due tocirrhosis of the liver or certain types of leukemia) and captures, or sequesters, more platelets from the circulation than normal. This could lead to thrombocytopenia.
In infants, many conditions similar to these listed above can lead toneonatal thrombocytopenia. There are also some rare genetic conditions that can also lead to thrombocytopenia in children at birth.
Pseudothrombocytopenia is term given to situations in which there is a falsely low platelet count on the blood smear reviewed by the laboratory. This can happen because of occasional clumping of the platelets together when the blood is drawn. Therefore, small number of individual platelets may be seen under the microscope, and this can be confused with true thrombocytopenia. A repeat blood draw, preferably in a tube which prevents clumping, typically solves this issue.
Platelet disorders lead to defects in primary hemostasis and produce signs and symptoms different from coagulation factor deficiencies (disorders of secondary hemostasis). The body’s reaction to vessel wall injury is rapid adhesion of platelets to the subendothelium. The initial hemostatic plug, composed primarily of platelets, is stabilized further by a fibrin mesh generated in secondary hemostasis. The arrest of bleeding in a superficial wound, such as the bleeding time wound, almost exclusively results from the primary hemostatic plug.
Hence, primary hemostatic disorders are characterized by prolonged bleeding time, and the characteristic physical examination findings are petechiae and purpura. In comparison, defects in secondary hemostasis result in delayed deep bleeding (eg, into muscles and joints) and the characteristic physical examination finding is hemarthrosis. Hemarthrosis and muscle hematomas are not present in primary hemostatic disorders.
Thrombocytopenia signs and symptoms may include:
- Easy or excessive bruising (purpura)
- Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on the lower legs
- Prolonged bleeding from cuts
- Bleeding from your gums or nose
- Blood in urine or stools
- Unusually heavy menstrual flows
- Enlarged spleen
Low platelet count is often discovered incidentally during routine blood work. Platelets are a component of the complete blood count (CBC) along with white blood cell and red blood cell counts. Pseudothrombocytopenia can be eliminated by repeating the CBC.
Investigation for low platelet count includes a comprehensive medical history and physical examination by the doctor. Review of all the medications, family history, and personal history of cancers, drug and alcohol use, bleeding problems, and other medical conditions (rheumatic diseases, liver problems, kidney disease) needs to be included in this evaluation. An enlarged spleen (splenomegaly), petechiae, and purpura are typically looked for on the physical examination in these patients.
Further diagnostic investigation for thrombocytopenia relies on a detailed review of the other values on the CBC (red cell count, hemoglobin, white blood cell count, mean platelet volume or MPV), the comprehensive blood chemistry panel (kidney function, liver function, electrolytes), blood coagulation panel (other components of the clotting system), and review of the blood smear under the microscope (looking for fragmented red cells, shape and size of white cells, red cells, platelets).
People with mild thrombocytopenia may not need treatment. For example, they may not have symptoms or the condition clears up on its own.
Some people develop severe or long-term (chronic) thrombocytopenia. Depending on what’s causing your low platelet count, treatments may include:
- Treating the underlying cause of thrombocytopenia. If your doctor can identify a condition or a medication that’s causing your thrombocytopenia, addressing that cause may clear up your thrombocytopenia
For example, if you have heparin-induced thrombocytopenia, your doctor will direct you to stop using heparin and prescribe a different blood-thinning drug. Your thrombocytopenia may persist for a week or more despite stopping all heparin therapy.
- Blood or platelet transfusions. If your platelet level becomes too low, your doctor can replace lost blood with transfusions of packed red blood cells or platelets.
- Medications. If your condition is related to an immune system problem, your doctor may prescribe drugs to boost your platelet count. The first-choice drug may be a corticosteroid. If that doesn’t work, he or she may try stronger medications to suppress your immune system.
- Surgery. If other treatment options don’t help, your doctor may recommend surgery to remove your spleen (splenectomy).
- Plasma exchange. Thrombotic thrombocytopenic purpura can result in a medical emergency requiring plasma exchange.