Immune Thrombocytopenia (ITP)

Snapshot

A 38-year-old man presents to his primary care physician’s office for episodes of epistaxis and gingival bleeding. He reports his symptoms began one day prior to presentation and has never occurred before. He denies starting any new medications. Social history is notable for current intravenous drug use. On physical exam, there is blood in the nares and mild bleeding of the gums. There are petechiae distal to where the blood pressure cuff was placed. Abdominal exam is unremarkable. A complete blood count is significant for a platelet count of 28,000/μL and peripheral blood smear demonstrates enlarged platelets.

Introduction

Clinical definition
- acquired immune-mediated destruction of otherwise normal platelets
Classification
- primary immune thrombocytopenia (ITP)
  - immune-mediated thrombocytopenia without an underlying condition
- secondary ITP
  - immune-mediated thrombocytopenia with an underlying condition (e.g., HIV infection)
Epidemiology
- demographics
  - 1-7 years of age commonly in children
Etiology
- primary ITP
  - unknown
- secondary ITP
  - autoimmune disorders
    - systemic lupus erythematosus
    - antiphospholipid syndrome
  - infection
    - HIV
    - hepatitis C virus
  - malignancy
    - chronic lymphocytic leukemia
  - vaccinations
Pathogenesis
- IgG antibodies directed against platelet membrane glycoproteins such as GPIIb/IIIa
a type II hypersensitivity reaction

Presentation

Studies

Making the diagnosis
- primary ITP
  - isolated thrombocytopenia (e.g., < 100,000/μL) without a known cause
- secondary ITP
isolated thrombocytopenia (e.g., < 100,000/μL) with an underlying condition (e.g., positive for HIV infection)

Differential

Hypersplenism
- distinguishing factor
  - splenomegaly
Liver disease
- distinguishing factor
  - elevated transaminases and hepatosplenomegaly
  - coagulation abnormalities may be present
Microangiopathic hemolytic process (e.g., thrombotic thrombocytopenic purpura)
- distinguishing factor
schistocytes are appreciated on peripheral blood smear

Treatment

Conservative
- observation
  - indication
    - in patients with a platelet count > 30,000/μL and no bleeding
Medical
- corticosteroids
  - indication
    - initial treatment for patients with a platelet count < 30,000/μL
- intravenous immunoglobulins (IVIG)
  - indication
    - for patients with a platelet count < 30,000/μL who have contraindications to corticosteroids, are refractory to corticosteroid treatment, or are bleeding or have a high risk of bleeding that will need a rapid increase in platelet count
Operative
- splenectomy
  - indication
second-line treatment for patients with refractory ITP

Complications