IDIOPATHIC THROMBOCYTOPENIA PURPURA (ITP)
DEFINITION:
A disorder characterized by a profound deficiency of platelets
due to the presence of platelet autoantibodies resulting in
petechiae, purpura, and mucocutaneous bleeding.
EPIDEMIOLOGY:
- incidence: ?
- age of onset:
- peak age: 2-4 years (acute ITP)
- <1 year and >10 years (chronic ITP)
- risk factors:
PATHOGENESIS:
- exposure to a viral infection -> production of platelet
auto-antibodies -> selective destruction of circulating
platelets - in 70% of cases acute ITP will present 1-4 weeks
(mean of 2 weeks) after exposure to the viral illness
2. Types of ITP
- ITP lasting less than 6 months
- typical history: sudden onset of bruising and petechiae in
a child in excellent health 1-4 weeks after a viral illness
- natural history is one of an acute, self-limiting disorder
resolving within 6 months
- is the most common cause of thrombocytopenia in childhood
2. Chronic ITP
- ITP lasting longer than 6 months
- should be checked for an underlying disorder
CLINICAL FEATURES:
- episode onset may be acute or insidious
- episode of bleeding may last 1-2 weeks then resolve
- in ITP, the liver, spleen, and lymph nodes are all normal
INVESTIGATIONS
- normal or elevated megakaryocytes
- normal granulocytic and erythrocytic series
- indicated to rule out aplastic anemia, platelet production
problem, or an infiltrative process
MANAGEMENT:
- review diagnosis, definition, and epidemiology
3. Treatment Options
- based upon the natural history of acute ITP after initial
onset (% in complete remission)
- relapses are unusual
2. Treatment
- indications for:
- symptomatic
- complications - severe hemorrhage, anemia, intracranial
bleed, chronic history of easy bruising
- best to initially observe all patients in hospital and
moniter the platelet count q12h to ensure that the counts are
not falling:
4. Goals of Therapy
- to prevent serious bleeding during the period of
thrombocytopenia, i.e., intracranial bleed
5. Management Strategies
- mechanism of action: IgG occupies Fc receptors on
reticuloendothelial cells resulting in improved survival of
opsonized platelets
- indications: acute ITP, elevated risk for intracranial
bleed, platelets <20,000
- dose: 0.8-1.0 g/kg/day (dose over 2 days is not more
effective)
- in 75% of cases, will elevate the platelet count (but has
no effect on the duration of ITP)
- target platelet count: >10
- side effects (in 3%):
- fever, vomiting, vertigo, headaches, lightheadedness
(slow-down infusion rate for these)
- hemolytic anemia
- anaphylaxis (seen in IgA deficient patients)
3. Corticosteroid Therapy
4. Splenectomy
- mechanism of action: bulk of antiplatelet antibodies are
synthesized in the spleen
- indications: chronic ITP with high risk of hemorrhage
- 65-88% of patients will remit immediately after
splenectomy
- platelet count will increase immediately after surgery and
may reach 1 million at 1-2 weeks postop.; if the platelet
count is >500,000, permanent remission is likely
- risks:
- post-splenectomy sepsis due to encapsulated organisms
(S. pneumoniae, H. flu, N. meningitidis); risk is greater in
those under 5 years of age
5. Others (for chronic refractory ITP)
6. Prognosis
- 80% acute ITP, 20% chronic ITP
2. Adolescent/Adult
- 20% acute ITP, 80% chronic ITP
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