When your blood has a low number of platelets—the small, disc-shaped cells that bind together when recognizing damaged blood vessels—the condition is called thrombocytopenia. This doesn’t automatically mean you have immune thrombocytopenia (ITP). There are many conditions that can lead to thrombocytopenia.

ITP is a diagnosis of exclusion. Since there is no definitive test to diagnose ITP, your doctor will rule out common causes of thrombocytopenia, such as an underlying illness or medications you or your child may be taking. This makes it important to know, or at least be aware of, other diseases that may be mistaken for or misdiagnosed as ITP to make certain you receive the best treatment for your condition.

blood cells3There are many possible causes of thrombocytopenia with the impact of symptoms ranging from trivial to life threatening. Distinguishing ITP from other conditions is usually determined by a physical examination, illness and medication history, assessment of a blood smear, additional blood tests and perhaps a bone marrow biopsy.

When thrombocytopenia is severe (a platelet count less than 20-30,000/microliter) and other obvious causes are ruled out, many doctors administer first-line conventional treatments for ITP, including corticosteroids (prednisone), anti-Rho(D) (anti-D) or intravenous immunoglobulin therapy (IVIG). A rapid response to these therapies supports the diagnosis of ITP; failure to respond to treatment should lead to further investigation of alternate causes of a low platelet count. Asking questions can help you and your doctor determine the correct diagnosis and best treatment.

Other Disorders That Could Cause Thrombocytopenia or Exist Alongside ITP

There are hundreds of disorders that may include thrombocytopenia among their symptoms. Some of these disorders arise from a combination of acquired or inherited factors, causing them to fall into several low-platelet disease categories. Thrombocytopenia believed to arise due to true ITP is referred to as primary ITP, whereas thrombocytopenia caused by other autoimmune or immune disorders are referred to as 'secondary ITP.' Thrombocytopenia caused by a genetic disorder is referred to as an inherited thrombocytopenia. To learn more about the difference between primary, secondary, and inherited ITP, visit the ITP & Genetics page.

The different categories of low-platelet diseases and helpful information for each are listed below: