Idiopathic Thrombocytopenic Purpura (Pearls)

• ITP differs in its presentation in adults vs children.  In children; acute ITP often follows viral illness and usually spontaneously resolves. However, in adults, it is more of a chronic disease and complete remission is uncommon.
• Suspect ITP in a patient with isolated thrombocytopenia with an otherwise normal smear.  The most important thing to remember is that ITP is a diagnosis of exclusion.  At the minimum, all patients should be ruled out for HIV and Hep C; all patients 60 years or older should have a bone marrow biopsy to exclude Myelodysplastic syndrome as well as other hematological malignancies. 
• Antiplatelet Antibodies are neither sensitive nor specific, and thus are not recommended to be checked.

Treatment: Generally, should treat all adults with platelet count <30 k, as remission is unlikely.  Patients with platelet count > 30k usually have a benign course without treatment.

1) Steroids – 1st line, patients usually respond within 2 weeks, but patients tend to recur once tapered.

2) IVIG – usually used with steroids; effect is seen within days and lasts weeks.  But again, this is a temporizing measure.

3) Splenectomy – thought to be the most effective therapy with the most durable response.  Induces long-term remission in ~66% of patients.  Of course, the problem is that often the patients who most urgently need splenectomy have severely low platelet counts, precluding surgery.  

4) Rituximab – short-term effectiveness in ~40%.  Usually reserved for patients who recur after splenectomy.

5) TPO Agonists – Romiplastin and Eltrombopag – the newest agents on the block - stimulate the bone marrow to increase platelet production.  Positive data from randomized controlled trials, but problem is that does not induce long-term response and so patients are often on them indefinitely.  There are also concerns about long-term safety, as patients can get deposition of reticulin in the bone marrow, potentially raising the risk of myelofibrosis and other malignancies.

(Chanu Rhee MD, 2/18/11)