A 5-year-old girl from Delhi presents with fever, headache, and myalgia for 3 days, followed by a maculopapular rash on the trunk and extremities. On examination, she has a positive tourniquet test and conjunctival injection. Laboratory investigations show platelet count 95,000/μL, haemoglobin 13.5 g/dL, haematocrit 40%, and normal liver enzymes. She is alert, vital signs are stable, and there is no warning sign. What is the most likely diagnosis?

Explanation

## Classification of Dengue in Children: DF vs DHF vs Severe Dengue ### Clinical Presentation Analysis **Key Point:** This child has: - Fever, headache, myalgia (classic dengue triad) - Maculopapular rash on trunk and extremities - Positive tourniquet test (petechiae after 40 mmHg pressure for 1 minute) - Conjunctival injection (dengue-specific sign) - **Stable vital signs, alert, no warning signs** - Mild thrombocytopenia (95,000/μL) but normal haematocrit (40%) ### WHO 2009 Dengue Classification | Feature | Dengue Fever (DF) | DHF Grade I | DHF Grade II | Severe Dengue | |---------|-------------------|-------------|--------------|---------------| | **Fever** | Yes | Yes | Yes | Yes | | **Hemorrhagic manifestations** | Positive tourniquet test OR petechiae | Positive tourniquet test | Spontaneous bleeding | Severe bleeding | | **Platelet count** | <100,000/μL | <100,000/μL | <100,000/μL | <100,000/μL | | **Hematocrit rise** | None | ≥20% | ≥20% | ≥20% | | **Plasma leakage signs** | None | Absent | Present (ascites, pleural effusion) | Present | | **Shock** | No | No | No | Yes (DSS) | | **Organ impairment** | No | No | No | Yes (hepatitis, encephalitis, renal) | **High-Yield:** The **key differentiator** between DF and DHF is **hematocrit rise ≥20%** (indicating plasma leakage). This child has: - Hematocrit 40% (normal for age; baseline ~38–40%) - No hematocrit rise - No warning signs (abdominal pain, persistent vomiting, lethargy, bleeding) - No plasma leakage signs (ascites, pleural effusion, hypotension) ### Why This Is Dengue Fever (DF) **Clinical Pearl:** DF is the **non-severe form** of dengue with fever, rash, and positive tourniquet test but **no plasma leakage** (normal Hct, no ascites, stable vitals). The positive tourniquet test alone does not diagnose DHF; **hematocrit rise is mandatory** for DHF classification. **Mnemonic:** **DF = Fever + Rash + Tourniquet, NO Hematocrit rise; DHF = DF + Hematocrit rise ≥20%** ### Dengue Hemorrhagic Fever (DHF) Grades - **Grade I:** Positive tourniquet test only, no spontaneous bleeding - **Grade II:** Spontaneous bleeding (gum, GI, skin, other sites) - **Grade III:** Shock (DSS) with hypotension - **Grade IV:** Profound shock with unmeasurable BP This child has a positive tourniquet test but **no hematocrit rise and no plasma leakage**, so she does NOT meet DHF criteria. ### Management of DF - Supportive care: paracetamol, fluids, rest - Avoid NSAIDs (increase bleeding risk) - Outpatient follow-up with repeat CBC on day 5–7 to confirm recovery - Counsel on warning signs (abdominal pain, vomiting, lethargy, bleeding) [cite:WHO Dengue Guidelines 2009, Park 26e Ch 7]