Definitions
acquired, quantitative, usually transient, immune-mediated disorder that results in accelerated destruction of platelets
Pathophysiology
antibodies against platelets being detected in 60%of patients.
The coating of platelets with IgG renders them susceptible to opsonization and phagocytosis by splenic macrophages.
The IgG autoantibodies are also thought to damage megakaryocytes,but this is thought to contribute only slightly to the decrease in platelet numbers.
Recent research: impaired production of the glycoprotein hormone thrombopoietin, which is the stimulant for platelet production, may be a contributing factor to the reduction in circulating platelets.
This observation has led to the development of a class of ITP-targeted drugs referred to as thrombopoietin receptor agonists.
Aetiology
Autoantibodies
⅔ of cases occurs several weeks after a preceding infectious illness (especially EBV)
may rarely be the initial presentation of HIV & SLE
Epidemiology
acute ITP is more common in children
Peak incidence: 4-8 years
M:F=1:1
Chronic ITP is more likely to develop in adolescent females
Presentation
petechiae & bruising with no other signs
Superficial nleeding
Splenomegaly in cases of splenic sequestration
intracranial haemorrharge is uncommon
Lack of positive exam
hx of viral illness and URTI
Investigation
Diagnosis of exclusion
FBC:
- low platelet (<20,000)
- normal Hb & WCC
- normal differential cell counts
- normal morpholology, except for large platelets
Bone marrow biopsy
- rule out leukemia if uncertain about ITP
- normal in ITP
- indicated if lymphadenopathy, hepatomegaly, protracted systemic symptoms, abnomal findings on CBC
- should also be done prior to steroid therapy, prior to splenectomy, or irresponsive to therapy
Consider ANA or HIV testing in high-risk pt
Management
No treatment if platelet > 30,000, observe and restrict activity
For platelet < 30,000
- corticosteroids - reduce production of antiplatelet antibodies
- IVIG blocks receptors on platelets, thereby decreasing destruction
- anti-RhD immunoglobulin (WinRho) decreases platelet destruction, used only for Rh-positive patients
- Platelet transfusions are only indicated if the platelet count is severely depressed with ongoing bleeding or significant risk of intracranial bleeding
Chronic ITP
- splenectomy if severe
- pulse steroids, IVIG, IV anti-D, rituximab, combination chemotherapy
Emergency management of life-threatening haemorrhage may include
- platelet transfusions
- IV steroids (30mg/kg, max dose of 1 gram for up to 3 doses)
- IVIG (1g/kg, repeat daily as clinically indicated for up to 5 doses)
- emergency splenectomy
Prognosis/Complications
90% of pt recover within a few months with or without treatment
<5% with acute ITP develop recurrent, acute thrombocytopenia
10% develop chronic ITP (ITP> 6months)
risk of collagen vascular disease or other underlying pathology is higher in chronic ITP
Major morbidity: intracranial haemorrhage
acquired, quantitative, usually transient, immune-mediated disorder that results in accelerated destruction of platelets
Pathophysiology
antibodies against platelets being detected in 60%of patients.
The coating of platelets with IgG renders them susceptible to opsonization and phagocytosis by splenic macrophages.
The IgG autoantibodies are also thought to damage megakaryocytes,but this is thought to contribute only slightly to the decrease in platelet numbers.
Recent research: impaired production of the glycoprotein hormone thrombopoietin, which is the stimulant for platelet production, may be a contributing factor to the reduction in circulating platelets.
This observation has led to the development of a class of ITP-targeted drugs referred to as thrombopoietin receptor agonists.
Aetiology
Autoantibodies
⅔ of cases occurs several weeks after a preceding infectious illness (especially EBV)
may rarely be the initial presentation of HIV & SLE
Epidemiology
acute ITP is more common in children
Peak incidence: 4-8 years
M:F=1:1
Chronic ITP is more likely to develop in adolescent females
Presentation
petechiae & bruising with no other signs
Superficial nleeding
Splenomegaly in cases of splenic sequestration
intracranial haemorrharge is uncommon
Lack of positive exam
hx of viral illness and URTI
Investigation
Diagnosis of exclusion
FBC:
- low platelet (<20,000)
- normal Hb & WCC
- normal differential cell counts
- normal morpholology, except for large platelets
Bone marrow biopsy
- rule out leukemia if uncertain about ITP
- normal in ITP
- indicated if lymphadenopathy, hepatomegaly, protracted systemic symptoms, abnomal findings on CBC
- should also be done prior to steroid therapy, prior to splenectomy, or irresponsive to therapy
Consider ANA or HIV testing in high-risk pt
Management
No treatment if platelet > 30,000, observe and restrict activity
For platelet < 30,000
- corticosteroids - reduce production of antiplatelet antibodies
- IVIG blocks receptors on platelets, thereby decreasing destruction
- anti-RhD immunoglobulin (WinRho) decreases platelet destruction, used only for Rh-positive patients
- Platelet transfusions are only indicated if the platelet count is severely depressed with ongoing bleeding or significant risk of intracranial bleeding
Chronic ITP
- splenectomy if severe
- pulse steroids, IVIG, IV anti-D, rituximab, combination chemotherapy
Emergency management of life-threatening haemorrhage may include
- platelet transfusions
- IV steroids (30mg/kg, max dose of 1 gram for up to 3 doses)
- IVIG (1g/kg, repeat daily as clinically indicated for up to 5 doses)
- emergency splenectomy
Prognosis/Complications
90% of pt recover within a few months with or without treatment
<5% with acute ITP develop recurrent, acute thrombocytopenia
10% develop chronic ITP (ITP> 6months)
risk of collagen vascular disease or other underlying pathology is higher in chronic ITP
Major morbidity: intracranial haemorrhage
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