First, ITP can be categorized as:
Primary: Primary ITP is due to autoimmune platelet destruction. In children, the majority of cases are primary ITP. Secondary: Secondary ITP is associated with another condition such as lupus, HIV, hepatitis C, or chronic lymphocytic leukemia.
Although treatments to resolve bleeding for primary and secondary ITP can be similar, the treatment of secondary ITP is focused on the underlying medical condition. Better control of the underlying medical condition can improve the thrombocytopenia.
Primary ITP then can be further subdivided into:
Newly diagnosed: Diagnosis to three months. Persistent: ITP that persists more than three months. Chronic: If persistent more than twelve months, it is labeled chronic. Refractory: This term is generally used to define ITP that requires treatment (patient has bleeding symptoms) that is refractory to first-line therapy (steroids, IVIG, WinRho) or splenectomy.
Despite the fact that the majority of adults diagnosed with primary ITP will go on to develop a chronic course, the majority will maintain a stable, safe platelet count (generally meaning more than 20,000 cells per microliters), where spontaneous bleeding is less likely.
These patients may still occasionally require additional courses of treatment. One example is surgery, where the platelet count often needs to be higher to prevent bleeding during the procedure.
Second-Line Treatments
The challenge is for those patients who continue to have bleeding despite first-line treatments. In years past, splenectomy was considered the mainstay of second-line therapy. Splenectomy works in two ways.
First, it removes the primary site of platelet destruction. Second, it removes some lymphocytes that produce anti-platelet antibodies live in the spleen. Removal of these lymphocytes may increase the lifespan of the platelets.
Splenectomy has a known track record with more than 85 percent of patients responding, the vast majority with normalization of platelet counts. Despite this success rate, splenectomy is not without its risks, especially the lifelong risk of overwhelming sepsis (serious bacterial infection).
Because of these risks, some physicians consider rituximab second-line therapy. Rituximab is an antibody that attaches itself to B lymphocytes (one of the white blood cells that makes antibodies), causing them to be destroyed.
With less anti-platelet antibody production from B lymphocytes, the platelets will not be destroyed. Rituximab is typically given as an IV infusion once weekly for four weeks, but sometimes fewer weeks may be given. The response to rituximab is more variable than splenectomy, with some patients having lasting responses but others relapsing.
Third-Line Treatments
Fortunately, now there are third-line therapies available for ITP. For many years, it was believed that in ITP, platelets were made normally in the bone marrow but were destroyed when released into circulation. Medical professionals now know that platelet production is also impaired. This knowledge resulted in the development of medications called thrombopoietin (TPO) receptor agonists.
Currently, there are two TPO receptor agonists available in the US, eltrombopag, and romiplostim. Eltrombopag is an oral medication taken daily and romiplostim is given once weekly as a subcutaneous injection.
Although eltrombopag may appear to be an easier therapy because it is taken by mouth, no foods containing calcium can be eaten for several hours before and after the dose. Once the maintenance dose is determined, adults may learn how to administer romiplostim at home.
TPO receptor agonists are considered chronic maintenance medications used to keep platelet count high enough to prevent bleeding. These medications can be used in both children and adults with chronic ITP.
As with many medical therapies, the order of first, second, and third-line treatment may vary based on individual patient characteristics. If you have questions or concerns about your therapy, you should discuss them with your physician.
