A 52-year-old man with a 20-year history of chronic hepatitis C presents to the outpatient clinic with complaints of easy bruising and epistaxis for 2 months. On examination: hepatomegaly (4 cm), ascites, and multiple ecchymoses. Laboratory investigations reveal: Hemoglobin 9.8 g/dL, WBC 3.2 × 10⁹/L, platelets 45 × 10⁹/L, INR 2.1, albumin 2.8 g/dL. Peripheral blood smear shows target cells, macrocytes, and occasional nucleated RBCs. What is the most likely cause of the thrombocytopenia in this patient?

Explanation

## Diagnosis: Splenic Sequestration Due to Portal Hypertension ### Clinical Context: Cirrhosis and Hypersplenism **High-Yield:** In a patient with chronic liver disease (cirrhosis from hepatitis C), **thrombocytopenia is most commonly caused by splenic sequestration (hypersplenism)**, not immune destruction or DIC. **Key Point:** Hypersplenism is the pathophysiologic consequence of portal hypertension leading to splenomegaly. The enlarged spleen sequesters up to 90% of circulating platelets, resulting in thrombocytopenia while bone marrow function remains intact. ### Diagnostic Clues Pointing to Splenic Sequestration | Feature | Significance | |---------|-------------| | **Hepatomegaly + ascites** | Evidence of advanced cirrhosis and portal hypertension | | **Mild thrombocytopenia (45 × 10⁹/L)** | Typically 20–50 × 10⁹/L in hypersplenism (not <10 × 10⁹/L) | | **Pancytopenia (Hb 9.8, WBC 3.2, Plt 45)** | Classic triad of hypersplenism | | **Target cells on smear** | Reflects liver synthetic dysfunction and cholestasis | | **Nucleated RBCs** | Indicates extramedullary hematopoiesis from chronic hemolysis | | **Macrocytes** | Often seen in chronic liver disease (folate/B12 deficiency, direct effect) | | **INR 2.1** | Reflects hepatic synthetic dysfunction (not DIC, where PT is prolonged acutely with low fibrinogen) | ### Why This Is NOT DIC **Warning:** DIC would present with: - Acute, severe thrombocytopenia (<20 × 10⁹/L) - Prolonged PT/aPTT with **low fibrinogen** (<100 mg/dL) - Schistocytes and fragmented RBCs on smear - Clinical signs of acute bleeding or sepsis This patient has **chronic** thrombocytopenia with normal fibrinogen (implied by stable INR) and no acute hemolysis. ### Pathophysiology of Hypersplenism ```mermaid flowchart TD A[Chronic Liver Disease/Cirrhosis]:::outcome --> B[Portal Hypertension]:::outcome B --> C[Splenic Congestion & Enlargement]:::outcome C --> D[Increased Splenic Sequestration]:::action D --> E[Thrombocytopenia]:::outcome D --> F[Leukopenia]:::outcome D --> G[Anemia]:::outcome E --> H[Pancytopenia = Hypersplenism]:::outcome ``` **Clinical Pearl:** The bone marrow in hypersplenism is **hyperactive** (not hypoplastic), attempting to compensate for peripheral destruction/sequestration. Bone marrow biopsy would show hypercellularity, not aplasia. ### Peripheral Blood Smear in Cirrhosis - **Target cells (codocytes):** Increased surface area-to-volume ratio due to cholestasis and abnormal lipid composition - **Macrocytes:** From folate deficiency, direct hepatotoxic effect, or alcohol-related changes - **Nucleated RBCs:** Immature RBCs released prematurely due to extramedullary hematopoiesis - **Schistocytes (absent):** Would indicate DIC or MAHA ### Clinical Management Implications **High-Yield:** Platelet transfusions in hypersplenism are often **ineffective** because transfused platelets are immediately sequestered by the enlarged spleen. Treatment focuses on: 1. Controlling portal hypertension (beta-blockers, variceal banding) 2. Liver transplantation (definitive) 3. Splenectomy (rarely, if thrombocytopenia is severe and refractory) [cite:Robbins 10e Ch 12] [cite:Harrison 21e Ch 298]