Idiopathic Thrombocytopenic Purpura

Detailed Overview

ITP results from pathogenic autoantibodies (usually IgG) targeting platelet surface glycoproteins (such as GPIIb/IIIa). These antibody-coated platelets are rapidly destroyed by macrophages in the spleen. Furthermore, these antibodies can inhibit megakaryocyte platelet production in the bone marrow. It presents acutely in children (often post-viral) and chronically in adults.

Epidemiology & Demographics

Incidence is 2-4 per 100,000 adults per year, and slightly higher in children. In adults, it is more common in females (2:1 ratio) mostly between ages 20-50. In children, it occurs equally between sexes, peaking at ages 2-5.

Etiological Mechanism

Idiopathic (Primary ITP) due to loss of self-tolerance. Secondary ITP can be triggered by HIV, Hepatitis C, H. pylori, SLE, or lymphoproliferative disorders like CLL.

Primary Causes

Autoimmune destruction (Primary ITP)

Viral infections (EBV, CMV, HIV, Hep C)

Helicobacter pylori infection

Autoimmune conditions (Systemic Lupus Erythematosus)

• Recent viral infection: Highly predictive of acute ITP in pediatric patients (occurs 1-3 weeks post-infection).
• Female sex: Women of childbearing age have higher rates of autoimmune diseases including ITP.
• H. pylori colonization: Endemic H. pylori infection is associated with secondary ITP.

IgG autoantibodies bind to platelet glycoproteins (GPIIb/IIIa, GPIb/IX). The Fc portions of these bound antibodies are recognized by Fc-gamma receptors on tissue macrophages, predominantly in the spleen, leading to phagocytosis and premature platelet clearance. Additionally, T-cell mediated cytotoxicity attacks megakaryocytes in the bone marrow, impairing compensatory platelet production. Bleeding risk increases significantly when platelet count falls below 20,000-30,000/microL.

Characteristic Clinical Presentation

• Easy bruising: Formation of large ecchymoses from minimal trauma.
• Petechiae: Pinpoint, non-blanching red/purple spots primarily on dependent areas like the lower legs.
• Mucosal bleeding: Spontaneous epistaxis (nosebleeds) or gingival bleeding when brushing teeth.
• Menorrhagia: Unusually heavy or prolonged menstrual bleeding.

Physical Examination Signs

• Petechiae, purpura, and ecchymoses on skin exam
• Blood blisters (wet purpura) in the oral mucosa (high risk for serious bleeding)
• Absence of splenomegaly (an enlarged spleen suggests a different diagnosis, like leukemia or liver disease)

• Intracranial Hemorrhage: The most feared complication, fatal but rare (<1% of cases), mostly when platelets <10,000/microL.
• Severe GI Bleeding: Spontaneous massive hemorrhage from the gastrointestinal tract.
• Treatment side effects: Corticosteroid-induced diabetes, osteoporosis, and immunosuppression.

Diagnostic Criteria & Guidelines

A diagnosis of exclusion. Isolated thrombocytopenia (platelets < 100,000/microL) with otherwise normal CBC and peripheral smear (absence of schistocytes, blasts). No clinically apparent associated conditions.

Differential Diagnosis

• Thrombotic Thrombocytopenic Purpura (TTP)
• Drug-Induced Thrombocytopenia (e.g., Heparin)
• Leukemia or Myelodysplastic Syndrome
• Pseudothrombocytopenia (platelet clumping in EDTA tubes)

Laboratory Tests & Biomarkers

• Platelet Count: Low (often < 20,000/microL in acute presentation).
• Hemoglobin and WBC: Normal (unless concurrent iron deficiency from bleeding).
• Peripheral Blood Smear: Normal RBC and WBC morphology; platelets are few and often large (megathrombocytes).
• HIV, HCV, H. pylori testing: Checked to rule out secondary causes of ITP.

Imaging Modalities & Findings

• Abdominal Ultrasound: Usually normal. Used to explicitly rule out splenomegaly, which would suggest portal hypertension or malignancy.

• Newly Diagnosed
  Diagnosis to 3 months.
• Persistent
  Lasting 3 to 12 months from diagnosis.
• Chronic
  Lasting more than 12 months.

Second-Line & Adjunctive Therapy

Thrombopoietin receptor agonists (TPO-RAs) like Eltrombopag 50 mg PO daily or Romiplostim 1 mcg/kg subQ weekly. Rituximab 375 mg/m2 IV weekly for 4 weeks. Fostamatinib (Syk inhibitor).

Surgical & Procedural Management

Laparoscopic splenectomy is considered for chronic, refractory ITP in patients who fail or cannot tolerate medical therapy, providing a long-term curative response in about 60-70% of patients.

Recommended Lifestyle Changes

• Strict avoidance of NSAIDs, aspirin, and other antiplatelet drugs.
• Avoid contact sports or activities with high risk of head trauma while platelets are low (<50,000/microL).
• Use a soft-bristled toothbrush to prevent gingival bleeding.

Patient Counseling & Advice

Warn patients to seek immediate emergency care for worst-headache-of-life, visual changes, or neurological symptoms, as these may herald intracranial hemorrhage. Review safe activity guidelines.

Follow-Up & Monitoring Schedule

Weekly CBC until platelet count stabilizes > 50,000/microL, then monthly or as needed. Monitor for signs of infection if on long-term steroids or post-splenectomy.

Preventive Strategies

No primary prevention. Secondary prevention of bleeding relies on maintaining platelets safely above 20,000-30,000/microL.

In children, 80% have spontaneous resolution within 6 months. In adults, the disease is usually chronic, but long-term survival is nearly normal with modern treatments.