## Distinguishing Dengue Fever from Dengue Hemorrhagic Fever ### Key Pathophysiologic Difference **Key Point:** The hallmark of DHF is **plasma leakage** due to increased vascular permeability, not merely thrombocytopenia or bleeding manifestations alone. ### Comparison Table: DF vs DHF | Feature | Dengue Fever (DF) | Dengue Hemorrhagic Fever (DHF) | | --- | --- | --- | | **Plasma leakage** | Absent | Present (critical discriminator) | | **Hemoconcentration** | Absent | Present (Hct rise ≥20%) | | **Pleural effusion/ascites** | Absent | May be present | | **Thrombocytopenia** | May occur | Present (≤100,000/µL) | | **Positive tourniquet test** | May occur | May occur | | **Petechial rash** | May occur | May occur | | **Bleeding manifestations** | Absent or mild | Present (mucosal, GI, or spontaneous) | ### Why Plasma Leakage is the Discriminator **High-Yield:** WHO classification of DHF requires **both**: 1. Thrombocytopenia (≤100,000/µL) **AND** 2. Evidence of plasma leakage (hemoconcentration, pleural effusion, ascites, or hypoproteinemia) Plasma leakage is the pathognomonic feature that separates DHF from uncomplicated DF. It occurs due to immune-mediated endothelial dysfunction and increased vascular permeability, typically during the critical phase (days 3–7). ### Clinical Pearl **Clinical Pearl:** A child with thrombocytopenia alone (without plasma leakage signs) has DF with thrombocytopenia, not DHF. Conversely, plasma leakage without bleeding (e.g., isolated ascites or pleural effusion) still qualifies as DHF. ### Mnemonic **PLASMA LEAKAGE = DHF:** **P**lasma leakage, **L**ow platelets, **A**scites/effusions, **S**evere bleeding, **M**ultiorgan dysfunction, **A**cute shock — these are the hallmarks of DHF, with plasma leakage being the essential discriminator. [cite:Park 26e Ch 8]
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