Viral exanthema
Viral exanthemas are widespread rashes caused by systemic viral infections. They often occur in children but can affect adults.
Recognising the pattern of rash, associated systemic features, and risk groups (especially pregnancy) is crucial for diagnosis and management.
🟠 Measles (Rubeola)
- 👶 Cause: Measles virus (respiratory droplets, highly contagious).
- ⚡ Clinical: High fever, "3 C’s" – cough, coryza, conjunctivitis. Koplik spots (pathognomonic). Rash starts on face → spreads downward.
- 🧪 Tests: Usually clinical; confirm with measles IgM or PCR if needed.
- 💊 Management: Supportive (fluids, antipyretics), Vitamin A, isolation (very infectious!).
🟢 Rubella (German Measles)
- 👶 Cause: Rubella virus (droplet spread).
- ⚡ Clinical: Mild fever, lymphadenopathy (suboccipital, postauricular). Pink maculopapular rash starting on face, less severe than measles.
- 🧪 Tests: Rubella IgM, PCR if diagnostic uncertainty.
- 💊 Management: Supportive. Key point: avoid contact with pregnant women due to risk of congenital rubella syndrome 🤰.
🔵 Varicella (Chickenpox)
- 👶 Cause: Varicella-zoster virus (droplet or direct contact).
- ⚡ Clinical: Fever + malaise followed by pruritic vesicles: “dew drop on a rose petal.” Rash starts trunk → spreads to face/limbs, crops at different stages.
- 🧪 Tests: Clinical; PCR from lesions if atypical.
- 💊 Management: Supportive with antihistamines. Acyclovir for immunocompromised/severe disease.
🌷 Roseola (Exanthem Subitum, HHV-6)
- 👶 Cause: HHV-6 (human herpesvirus 6).
- ⚡ Clinical: High fever (3–5 days), followed by sudden pink rash once fever resolves. Affects infants/toddlers.
- 🧪 Tests: Clinical; PCR rarely needed.
- 💊 Management: Supportive, antipyretics for fever. Reassure parents (benign course).
🟥 Erythema Infectiosum (Fifth Disease)
- 👶 Cause: Parvovirus B19 (droplet spread).
- ⚡ Clinical: “Slapped cheek” facial rash, followed by lacy reticular rash on limbs. Mild systemic features. May trigger aplastic crisis in haemolytic anaemias.
- 🧪 Tests: Clinical; IgM serology if required.
- 💊 Management: Supportive. Key: avoid contact with pregnant women (risk of hydrops fetalis).
🖐️ Hand, Foot, and Mouth Disease (HFMD)
- 👶 Cause: Coxsackievirus / enterovirus (direct contact, faeco-oral).
- ⚡ Clinical: Fever, sore throat, vesicles on hands, feet, and mouth ulcers. Young children most affected.
- 🧪 Tests: Clinical; PCR if severe.
- 💊 Management: Supportive, hydration (oral lesions may cause painful swallowing).
📌 Exam & OSCE Pearls
- 🌡️ Measles: Koplik spots = pathognomonic.
- 🌸 Rubella: Concern = pregnancy exposure.
- 💧 Varicella: Vesicles at different stages in same area.
- 🎭 Roseola: Rash appears after fever subsides.
- 👋 Erythema infectiosum: “Slapped cheek” appearance.
- 🖐️ HFMD: Classic distribution = hands, feet, and mouth.
