A 28-year-old woman from rural Maharashtra presents with a 3-day history of severe epistaxis and gum bleeding. She reports easy bruising for the past 2 weeks and denies any recent trauma or medication use. On examination, she has petechiae on her lower extremities and oral mucosa. Laboratory findings show: Hemoglobin 9.2 g/dL, WBC 6,500/μL, platelets 8,000/μL, PT 12 s (normal), aPTT 32 s (normal), bleeding time 8 min (prolonged). Bone marrow examination shows normocellular marrow with increased megakaryocytes. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Immune Thrombocytopenia (ITP) ### Key Clinical Features **Key Point:** ITP is characterized by isolated thrombocytopenia (<50,000/μL) with normal coagulation studies and increased bone marrow megakaryocytes — indicating peripheral destruction rather than impaired production. ### Diagnostic Criteria Met | Feature | Finding | Significance | |---------|---------|---------------| | **Platelet count** | 8,000/μL | Severe thrombocytopenia | | **PT/aPTT** | Normal | Rules out coagulopathy | | **Bleeding time** | Prolonged | Reflects platelet dysfunction/low count | | **Bone marrow** | Increased megakaryocytes | Indicates compensatory response to peripheral destruction | | **Clinical presentation** | Mucocutaneous bleeding, petechiae | Typical of severe ITP | ### Pathophysiology 1. Autoimmune destruction of platelets by anti-platelet IgG antibodies 2. Spleen acts as primary site of platelet sequestration and destruction 3. Bone marrow responds with increased megakaryopoiesis but cannot compensate for rapid peripheral loss 4. Coagulation cascade remains intact (normal PT/aPTT) ### Why This Is ITP and Not Other Conditions **High-Yield:** The combination of **isolated thrombocytopenia + normal coagulation studies + increased bone marrow megakaryocytes** is pathognomonic for ITP. **Clinical Pearl:** In ITP, the bleeding time is prolonged because bleeding time depends on platelet count and function — with <10,000/μL platelets, hemostasis is severely compromised despite normal platelet morphology. ### Management Approach ```mermaid flowchart TD A[Severe ITP<br/>Platelet <30,000/μL<br/>with bleeding]:::outcome --> B{First-line therapy?}:::decision B -->|Corticosteroids| C[Prednisolone 1 mg/kg/day]:::action B -->|IVIG| D[2 g/kg over 3-5 days]:::action C --> E[Response in 3-7 days]:::outcome D --> F[Rapid response<br/>24-48 hours]:::outcome E --> G{Sustained remission?}:::decision G -->|Yes| H[Taper and monitor]:::action G -->|No| I[Splenectomy or<br/>second-line agents]:::action ``` **Key Point:** First-line treatment for symptomatic ITP with severe thrombocytopenia is **corticosteroids ± IVIG**. Splenectomy is reserved for corticosteroid-responsive patients who relapse on tapering or require unacceptable doses. [cite:Harrison 21e Ch 139]