A 28-year-old woman from Kerala presents with fever, myalgia, and severe joint pain (polyarthralgia) affecting wrists, ankles, and knees for 5 days. She also reports a maculopapular rash on the trunk and extremities. Serology shows IgM antibodies against chikungunya virus. Regarding the clinical and laboratory features of chikungunya infection, all of the following are true EXCEPT:

Explanation

## Clinical and Laboratory Features of Chikungunya Infection ### Correct Statements **Key Point:** Chikungunya arthralgia is characteristically **symmetrical** and affects small joints (wrists, ankles, interphalangeal joints). Crucially, post-chikungunya chronic arthralgia (PCAA) occurs in 10–60% of infected individuals and can persist for months to years, sometimes indefinitely. This chronic phase is a hallmark distinguishing feature from dengue. [cite:Harrison 21e Ch 297] **Key Point:** Chikungunya virus (genus Alphavirus, family Togaviridae) replicates in **endothelial cells, fibroblasts, and muscle cells**. This tropism leads to vasculitis, myositis, and the characteristic maculopapular rash. The virus is notably **cytopathic** in cell culture, unlike dengue. [cite:Robbins 10e Ch 8] **Key Point:** **IgM antibodies** are the diagnostic marker for acute chikungunya infection, appearing within **3–5 days** of symptom onset and persisting for **1–2 months**. IgG appears later (around day 7–10) and provides long-term immunity. IgM positivity in the acute phase is the gold standard for diagnosis. [cite:Park 26e Ch 3] ### Incorrect Statement (The Answer) **High-Yield:** Hemorrhagic manifestations and thrombocytopenia are **NOT** the most common severe complications in chikungunya. In fact: - **Hemorrhagic fever is RARE** in chikungunya (unlike dengue hemorrhagic fever, which is common) - **Thrombocytopenia is mild** when present and does not correlate with severity - **Most common severe complications** in chikungunya include: - Neurological: meningoencephalitis, Guillain-Barré syndrome (rare but documented) - Cardiac: myocarditis (rare) - Hemorrhagic manifestations occur in <5% of cases The statement that hemorrhagic manifestations and thrombocytopenia are the **most common severe complications** occurring in **>50% of hospitalized patients** is **factually incorrect**. ### Comparative Clinical Features: Dengue vs. Chikungunya | Feature | Dengue | Chikungunya | | --- | --- | --- | | **Fever pattern** | Biphasic ("saddle-back") | Monophasic, high | | **Joint involvement** | Mild arthralgia | Severe, symmetrical polyarthralgia | | **Chronic arthralgia** | Rare | Common (10–60%) | | **Hemorrhagic manifestations** | Common (DHF/DSS) | **Rare** (<5%) | | **Thrombocytopenia** | Marked, prognostic | Mild/absent | | **Rash** | Maculopapular, centripetal | Maculopapular, centrifugal | | **Myositis/muscle pain** | Mild | Prominent | **Clinical Pearl:** The **absence of hemorrhagic fever** in chikungunya despite high viremia is a key clinical distinguishing feature. Dengue causes endothelial dysfunction and increased vascular permeability (plasma leak), whereas chikungunya causes direct tissue inflammation without vascular leak. This is why dengue requires careful fluid management (risk of DHF/DSS), while chikungunya is managed supportively with NSAIDs for arthralgia.