last authored: April 2012, Dave LaPierre
Immune thrombocytopenic purpura (ITP) is the most common cause of isolated thrombocytopenia, or level of platelets <100,000/ml. It is a diagnosis of exclusion, and other causes of low platelets, such as disease or toxic exposure must be ruled out.
Gordon is a 13 year-old boy who is brought the emergency department because of bruising and nosebleeds that began one day ago. He feels, and appears otherwise well. Bloodwork reveals a platelet count of 15,000/ml.
Acute ITP usually begins at age 2-6 with abrupt duration, lasts for weeks, and spontaneously remits in >80% of cases. Counts can often decrease to less than 20,000. Cases very frequently follow infection with varicella, CMV, EBV, or other viruses.
Chronic ITP peaks at ages 20-40, has insidious onset, and lasts months to years, with rare remission. Platelet count tends to be 30,000-80,000. Cases can follow conditions including:
ITP follows platelet destruction and increased decreased levels of production.
Coating of platelets by antibodies (IgG, often against glycoproteins IIB-IIIa or Ib-IX) leads to their phagocytosis by splenic macrophages. These antibodies are also thought to reduce megakaryocyte production.
Acute ITP often begins as sudden onset petechiae, purpura, and epistaxis in an otherwise well child.
Symptoms to ask about include:
Evaulate for evidence of bleeding:
No lymphadenopathy or hepatosplenomegaly are present; if the spleen is enlarged, the diagnosis is wrong!
In order to rule out other conditions, order:
Bone marrow biopsy should be done in patients over 60, or if cases are refractory. It can show increased number of megakaryocytes.
Serum platelet-associated IgG testing may be done, but is not helpful for guiding treatment decisions, and is complicated by high levels of false positive and negative testing.
A CT of the head should be done to rule out bleeding if signs and symptoms suggest.
Diagnosis is one of exclusion. It is important to rule out other causes of thrombocytopenia, including:
Patients should avoid contact sports or other activities that could increase risk of injury. ASA, clopidogrel, and other platelet-inhibiting drugs should be avoided.
Treatment should be instituted in the following cases:
Patients should be admitted if they are actively bleeding, or if counts are <20,000 (which increases risk of bleeding).
Oral steroids (2-6 weeks, then tapered) are the first line and are indicated for:
Platelet counts should be repeated after 1-2 days, and monitored weekly while on steroid treatment. If there is no change, diagnosis should be confirmed with further evaluation (including by bone marrow aspiration).
IV immune globulin or Anti-Rh can be used if steroids fail.
Splenectomy is the next best management and may be necessary if bleeding is life-threatening. Accessory spleen should be considered if splenectomy is not curative. Following splenectomy, specific vaccination and antibiotic prophylaxis should be provided.
Other treatments to consider include:
Platelet transfusions are not routinely helpful, as antibodies will simply inactivate them. However, in situations with significant bleeding, they can be life-saving.
Over 80% of cases of acute ITP are recovered within 6 months. Between 5-15% of patients proceed to chronic ITP.
Chronic ITP cases spontaneously recover in 10-20% of cases. The majority of these cases see persistent low levels for months or years. Approximately 10% of cases are resistent to all therapy, including medication and splenectomy.
Mortality is rare, with rates at 1-2%. Complications include:
Godeau B, Provan D, Bussel J. 2007. Immune thrombocytopenic purpura in adults. Curr Opinion in Hematology. 14:535-56.
Tarantino MD. 2006. The threatment of immune thrombocytopenic purpura in children. Curr Opinion in Hematology. 5:89-94.