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Viral exanthema

Medicine > Infection

Background knowledge 🧠

Definition

  • Viral exanthema refers to a widespread rash commonly occurring in children, caused by viral infections.
  • Often presents alongside systemic symptoms like fever and malaise.
  • Can be a feature of specific viral illnesses or a non-specific viral presentation.

Epidemiology

  • Most common in children under 10 years of age.
  • Peak incidence during late winter to early spring.
  • Highly contagious in the prodromal phase of viral infections.
  • Most cases are self-limiting.

Aetiology and Pathophysiology

  • Caused by a variety of viruses, including measles, rubella, human herpesvirus 6 (HHV-6), and enteroviruses.
  • Viral replication and immune response contribute to the development of the rash.
  • The rash typically results from immune complex deposition or direct viral invasion of the skin.
  • Can be associated with other systemic manifestations, depending on the causative virus.

Types

  • Measles: Erythematous maculopapular rash, Koplik spots.
  • Rubella: Pink maculopapular rash, postauricular lymphadenopathy.
  • Roseola: Sudden high fever followed by a maculopapular rash.
  • Erythema infectiosum: Slapped cheek appearance, lacy reticular rash.
  • Varicella (chickenpox): Vesicular rash in different stages of healing.
  • Hand, foot, and mouth disease: Vesicular rash on hands, feet, and oral mucosa.

Clinical Features 🌡️

Symptoms

  • Fever often precedes rash development.
  • Malaise, headache, and myalgia are common.
  • Specific symptoms depend on the causative virus, e.g., cough and coryza in measles.
  • Pruritus may be present, especially in varicella.
  • Conjunctivitis is common in measles and rubella.

Signs

  • Erythematous maculopapular rash is most common.
  • Distribution varies: often begins on the face and spreads centrifugally.
  • Koplik spots in measles, Forchheimer spots in rubella.
  • Lymphadenopathy may be present, particularly in rubella.
  • Vesicular lesions in chickenpox and hand, foot, and mouth disease.

Investigations 🧪

Tests

  • Clinical diagnosis is often sufficient, based on history and examination.
  • Serology: IgM and IgG antibodies for specific viruses (e.g., measles, rubella).
  • PCR testing for viral DNA/RNA may be useful in atypical or severe cases.
  • Full blood count: Lymphopenia in some viral infections.
  • Swabs or vesicle fluid analysis for viruses like varicella or herpes simplex.

Management 🥼

Management

  • Symptomatic treatment: Antipyretics (e.g., paracetamol), hydration.
  • Antivirals: Consider in severe or immunocompromised cases (e.g., acyclovir for varicella).
  • Isolation during contagious period to prevent spread.
  • Good hygiene practices: Hand washing, avoiding contact with vulnerable populations.
  • No specific treatment required for most viral exanthems, as they are self-limiting.

Complications

  • Rare but may include encephalitis (measles), myocarditis (enteroviruses).
  • Secondary bacterial infections (e.g., cellulitis in varicella).
  • Pneumonia in severe cases or in immunocompromised patients.
  • Congenital rubella syndrome if infection occurs during pregnancy.

Prognosis

  • Generally excellent in healthy children with full recovery.
  • Prognosis depends on the specific virus and patient comorbidities.
  • Complications are rare but more common in immunocompromised individuals.
  • Most exanthems are self-limiting within 7-10 days.

Key Points

  • Viral exanthems are common in paediatrics and usually benign.
  • Measles, rubella, and varicella are vaccine-preventable.
  • Management is primarily supportive, focusing on symptom relief.
  • Complications are rare but can be severe, especially in at-risk populations.

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Infection