A 28-year-old woman presents to the emergency department with a 3-day history of severe mucosal bleeding, including epistaxis, gingival bleeding, and menorrhagia. She reports no prior bleeding history. On examination, she is pale with petechiae and ecchymoses over the lower extremities. Laboratory investigations reveal: Hemoglobin 8.2 g/dL, Platelet count 8,000/μL, PT 12 s (normal), aPTT 32 s (normal), Fibrinogen 280 mg/dL (normal). Peripheral blood smear shows no schistocytes. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Immune Thrombocytopenia (ITP) ### Key Distinguishing Features **Key Point:** ITP is a diagnosis of exclusion characterized by isolated thrombocytopenia with normal coagulation studies and normal fibrinogen in the absence of other causes. ### Why ITP Fits This Case 1. **Isolated thrombocytopenia** — Platelet count 8,000/μL with normal PT, aPTT, and fibrinogen rules out consumptive coagulopathy (DIC). 2. **No microangiopathic hemolytic anemia** — Hemoglobin is low due to bleeding, not hemolysis. Peripheral smear shows no schistocytes, excluding TTP/HUS. 3. **Mucosal bleeding pattern** — Typical for severe thrombocytopenia; no systemic features (fever, renal dysfunction, neurological symptoms) that would suggest TTP. 4. **Normal coagulation cascade** — PT and aPTT normal; fibrinogen preserved. This excludes DIC, where both would be prolonged and fibrinogen low. ### Differential Diagnosis Table | Feature | ITP | TTP | DIC | | --- | --- | --- | --- | | Platelet count | Very low (<20k) | Very low (<20k) | Low | | PT/aPTT | Normal | Normal | Prolonged | | Fibrinogen | Normal | Normal | Low | | Schistocytes | Absent | Present | May be present | | Fever | No | Yes (classic) | Variable | | Renal dysfunction | No | Yes (classic) | Yes | | Neurological symptoms | No | Yes (classic) | No | **High-Yield:** The pentad of TTP (thrombocytopenia, microangiopathic hemolytic anemia, fever, renal dysfunction, neurological symptoms) is rarely complete; however, schistocytes on blood smear are the hallmark finding. Absence of schistocytes strongly argues against TTP. ### Clinical Pearl **Clinical Pearl:** ITP typically presents acutely in young adults with mucosal bleeding and severe thrombocytopenia. The diagnosis is confirmed by exclusion of secondary causes (SLE, antiphospholipid syndrome, HIV, HCV) and absence of splenomegaly. Bone marrow examination is not routinely needed in young patients with typical presentation. ### Management Implications First-line treatment includes corticosteroids (prednisolone 1 mg/kg/day) and IVIG for rapid platelet increment. Platelet transfusion is reserved for life-threatening bleeding.