Idiopathic Thrombocytopenic Purpura in Children
Introduction to Idiopathic Thrombocytopenic Purpura in Children
Idiopathic Thrombocytopenic Purpura (ITP), also known as Immune Thrombocytopenia, is an acquired autoimmune disorder characterized by isolated thrombocytopenia (platelet count <100,000/μL) in the absence of other causes or disorders that may be associated with thrombocytopenia.
Key points:
- Most common cause of acute thrombocytopenia in otherwise healthy children
- Peak incidence between 2-5 years of age
- Slightly more common in boys in younger age groups, but equal gender distribution in adolescents
- Classified as:
- Newly diagnosed: <3 months duration
- Persistent: 3-12 months duration
- Chronic: >12 months duration
- 80% of children have self-limited disease that resolves within 6-12 months
Pathophysiology of ITP in Children
ITP is an autoimmune disorder characterized by both increased platelet destruction and impaired platelet production:
- Autoantibody production:
- B cells produce autoantibodies (primarily IgG) against platelet membrane glycoproteins (most commonly GPIIb/IIIa)
- Often triggered by a preceding viral infection or vaccination
- Increased platelet destruction:
- Antibody-coated platelets are recognized and phagocytosed by macrophages in the spleen and liver
- Platelet lifespan is drastically reduced from 7-10 days to hours
- Impaired platelet production:
- Autoantibodies also bind to megakaryocytes in the bone marrow
- This leads to decreased platelet production and release
- T cell dysregulation:
- Imbalance between T helper cells and regulatory T cells
- Contributes to the loss of tolerance and persistence of autoantibody production
The combination of increased destruction and impaired production results in the characteristic thrombocytopenia seen in ITP.
Clinical Presentation of ITP in Children
The clinical presentation of ITP in children can vary widely, from asymptomatic cases to severe bleeding:
- Common symptoms:
- Sudden onset of petechiae and purpura, often on the lower limbs
- Easy bruising
- Mucosal bleeding (e.g., epistaxis, gingival bleeding)
- Less common symptoms:
- Gastrointestinal bleeding
- Hematuria
- Heavy menstrual bleeding in adolescent girls
- Rare but serious:
- Intracranial hemorrhage (occurs in <0.5% of children with ITP)
Important clinical features:
- Often preceded by a viral infection or vaccination (1-4 weeks prior)
- Abrupt onset in previously healthy child
- No hepatosplenomegaly (if present, consider alternative diagnoses)
- No systemic symptoms (fever, weight loss, bone pain) that might suggest malignancy
- Bleeding severity generally correlates with platelet count, but not always
The absence of other cytopenias and systemic symptoms helps differentiate ITP from other causes of thrombocytopenia.
Diagnosis of ITP in Children
The diagnosis of ITP is primarily one of exclusion. The following steps are typically involved:
- History and Physical Examination:
- Assess for recent infections, vaccinations, medications
- Family history of bleeding disorders or autoimmune diseases
- Thorough physical exam to look for bleeding signs and rule out lymphadenopathy or organomegaly
- Laboratory Tests:
- Complete Blood Count (CBC) with peripheral blood smear
- Isolated thrombocytopenia (platelets <100,000/μL)
- Normal red and white blood cell counts and morphology
- Coagulation studies (PT, PTT, fibrinogen) - typically normal in ITP
- Blood type and Rh factor (relevant for potential treatments)
- Complete Blood Count (CBC) with peripheral blood smear
- Additional Tests (based on clinical presentation):
- Antinuclear antibody (ANA) to screen for autoimmune disorders
- HIV and hepatitis C testing in adolescents
- Helicobacter pylori testing in areas with high prevalence
- Bone Marrow Examination:
- Not routinely recommended in typical cases
- Consider if atypical features present (e.g., other cytopenias, abnormal WBC morphology)
- Antiplatelet Antibody Testing:
- Not recommended for routine diagnosis due to poor sensitivity and specificity
The diagnosis of ITP can be made if:
- Isolated thrombocytopenia is present
- History, physical examination, and blood smear are consistent with ITP
- Other causes of thrombocytopenia are excluded
Management of ITP in Children
The management of ITP in children is individualized based on the severity of thrombocytopenia, presence of bleeding, and patient factors. The main approaches include:
- Observation ("Watch and Wait"):
- Suitable for children with mild thrombocytopenia (>20,000/μL) and no significant bleeding
- Regular monitoring of platelet counts
- Education about avoiding trauma and contact sports
- Pharmacological Treatments:
- First-line therapies:
- Corticosteroids (e.g., prednisone, dexamethasone)
- Typical dose: Prednisone 2-4 mg/kg/day for 1-2 weeks, then taper
- Intravenous Immunoglobulin (IVIG)
- Dose: 0.8-1 g/kg as a single infusion
- Anti-D Immunoglobulin (for Rh-positive patients)
- Dose: 50-75 μg/kg as a single dose
- Corticosteroids (e.g., prednisone, dexamethasone)
- Second-line therapies (for chronic or refractory ITP):
- Rituximab
- Thrombopoietin receptor agonists (e.g., eltrombopag, romiplostim)
- Other immunosuppressants (e.g., mycophenolate mofetil, sirolimus)
- First-line therapies:
- Emergency Management:
- Platelet transfusions for severe bleeding or extremely low platelet counts
- High-dose methylprednisolone or IVIG
- Splenectomy:
- Rarely used in children
- Considered only in severe, chronic cases refractory to medical management
- Supportive Care:
- Avoid medications that affect platelet function (e.g., NSAIDs, aspirin)
- Iron supplementation if iron-deficiency anemia develops
- Psychosocial support for children and families
Treatment decisions should be made in consultation with the child and family, considering the risks and benefits of each approach.
Prognosis of ITP in Children
The prognosis for children with ITP is generally favorable:
- Acute ITP:
- Spontaneous remission occurs in 70-80% of children within 6 months
- Excellent long-term prognosis
- Chronic ITP (duration >12 months):
- Occurs in 20-30% of children with ITP
- Remission rates of 50-60% by 5 years after diagnosis
- Bleeding risk:
- Severe bleeding is rare (<3% of cases)
- Intracranial hemorrhage occurs in <0.5% of children
- Quality of life:
- Most children have good quality of life, especially after the acute phase
- Chronic ITP may have more impact on daily activities and psychological well-being
- Long-term follow-up:
- Regular monitoring of platelet counts
- Adjustment of treatment as needed
- Transition of care for adolescents with chronic ITP
Factors associated with increased likelihood of chronic ITP include:
- Age >10 years at onset
- Insidious onset of symptoms
- No preceding infection or vaccination
- Higher platelet counts at presentation (>20,000/μL)
Overall, the majority of children with ITP have a good prognosis, with minimal long-term complications and a high likelihood of spontaneous remission.
Idiopathic Thrombocytopenic Purpura in Children
- QUESTION: What is the primary mechanism of thrombocytopenia in ITP?
ANSWER: Autoantibody-mediated destruction of platelets - QUESTION: What is the most common age group for acute ITP in children?
ANSWER: 2-5 years old - QUESTION: Which of the following is NOT a typical presenting symptom of ITP in children?
ANSWER: Fever - QUESTION: What is the most common preceding event in acute childhood ITP?
ANSWER: Viral infection - QUESTION: What is the typical platelet count in a child with newly diagnosed ITP?
ANSWER: Less than 20,000/µL - QUESTION: Which of the following is the gold standard for diagnosing ITP?
ANSWER: There is no specific diagnostic test; it is a diagnosis of exclusion - QUESTION: What percentage of children with acute ITP recover spontaneously within 6 months?
ANSWER: Approximately 80% - QUESTION: Which of the following is NOT a first-line treatment option for acute ITP in children?
ANSWER: Splenectomy - QUESTION: What is the mechanism of action of intravenous immunoglobulin (IVIG) in treating ITP?
ANSWER: Blockade of Fc receptors on macrophages - QUESTION: Which of the following is a potential side effect of high-dose corticosteroid treatment in ITP?
ANSWER: Avascular necrosis - QUESTION: What is the definition of chronic ITP in children?
ANSWER: Thrombocytopenia persisting for more than 12 months - QUESTION: Which of the following is NOT a typical finding in the bone marrow of ITP patients?
ANSWER: Decreased megakaryocytes - QUESTION: What is the most serious complication of ITP in children?
ANSWER: Intracranial hemorrhage - QUESTION: Which of the following medications can exacerbate thrombocytopenia in ITP patients?
ANSWER: Aspirin - QUESTION: What is the role of thrombopoietin receptor agonists in treating ITP?
ANSWER: To stimulate platelet production - QUESTION: Which of the following is a contraindication for splenectomy in children with chronic ITP?
ANSWER: Age less than 5 years - QUESTION: What is the typical pattern of bleeding in ITP?
ANSWER: Mucocutaneous bleeding - QUESTION: Which of the following is NOT a typical finding in the peripheral blood smear of ITP patients?
ANSWER: Giant platelets - QUESTION: What is the estimated incidence of ITP in children?
ANSWER: 4-5 cases per 100,000 children per year - QUESTION: Which of the following is a potential trigger for ITP in children?
ANSWER: Recent vaccination - QUESTION: What is the role of rituximab in treating chronic ITP in children?
ANSWER: To deplete B lymphocytes and reduce autoantibody production - QUESTION: Which of the following is a potential complication of splenectomy in ITP patients?
ANSWER: Increased risk of sepsis with encapsulated organisms - QUESTION: What is the term for the presence of petechiae and purpura in ITP?
ANSWER: Cutaneous purpura - QUESTION: Which of the following is NOT a typical feature of ITP in children?
ANSWER: Splenomegaly - QUESTION: What is the typical duration of effect for IVIG treatment in ITP?
ANSWER: 2-4 weeks - QUESTION: Which of the following is a potential trigger for relapse in children with ITP?
ANSWER: Viral infections - QUESTION: What is the recommended platelet count threshold for most invasive procedures in ITP patients?
ANSWER: 50,000/µL - QUESTION: Which of the following is NOT a typical indication for treatment in childhood ITP?
ANSWER: Asymptomatic thrombocytopenia with platelet count >30,000/µL - QUESTION: What is the role of antiplatelet antibody testing in diagnosing ITP?
ANSWER: It is not routinely recommended due to low sensitivity and specificity - QUESTION: Which of the following is a potential long-term complication of chronic ITP in children?
ANSWER: Impaired quality of life due to activity restrictions
