Viral Exanthems

Introduction | Common Viral Exanthems | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Viral exanthems are rashes or eruptions on the skin that are associated with viral infections. They are commonly seen in children but can occur at any age. Viral exanthems often present with other systemic symptoms such as fever, malaise, and upper respiratory symptoms. The most common viral exanthems include measles, rubella, roseola, erythema infectiosum (fifth disease), and varicella (chickenpox).

Common Viral Exanthems

Here is an overview of the most common viral exanthems:

1. Measles (Rubeola)

Caused by the measles virus, this exanthem is highly contagious and presents with a characteristic rash, cough, coryza, and conjunctivitis, followed by the appearance of Koplik's spots in the mouth. The rash typically starts on the face and spreads downward.

2. Rubella (German Measles)

Rubella is a milder viral illness than measles, caused by the rubella virus. It presents with a fine, pink maculopapular rash that begins on the face and spreads to the trunk and limbs. Lymphadenopathy, particularly behind the ears and at the back of the neck, is common.

3. Roseola (Exanthem Subitum)

Roseola is caused by human herpesvirus 6 (HHV-6) and typically affects infants and young children. It presents with a high fever lasting 3-5 days, followed by a sudden onset of a pink maculopapular rash as the fever subsides. The rash usually starts on the trunk and spreads to the limbs.

4. Erythema Infectiosum (Fifth Disease)

Caused by parvovirus B19, this exanthem is characterised by a "slapped cheek" appearance on the face, followed by a lacy, reticular rash on the trunk and limbs. It is often associated with mild fever and joint pain.

5. Varicella (Chickenpox)

Varicella-zoster virus (VZV) causes chickenpox, which presents with a pruritic vesicular rash that progresses from macules to papules, vesicles, and crusts. The rash typically appears in successive crops, leading to lesions in various stages of development. It is often accompanied by fever and malaise.

6. Hand, Foot, and Mouth Disease

Caused by coxsackievirus, this illness presents with a vesicular rash on the hands, feet, and oral mucosa. It is often associated with fever, sore throat, and reduced appetite. The rash typically involves the palms, soles, and inside of the mouth.

Clinical Presentation

The clinical presentation of viral exanthems can vary depending on the causative virus, but common features include:

• Fever: Most viral exanthems are preceded or accompanied by fever, which can vary in severity.
• Rash: The rash is typically widespread, affecting multiple body areas. The type of rash (maculopapular, vesicular, etc.) and its distribution are key to identifying the underlying virus.
• Systemic Symptoms: These may include malaise, headache, sore throat, cough, conjunctivitis, and lymphadenopathy.
• Prodromal Symptoms: Some exanthems, like measles, have a prodrome with specific features (e.g., cough, coryza, conjunctivitis) before the rash appears.

Diagnosis

Diagnosis of viral exanthems is typically clinical, based on the characteristic appearance of the rash and associated symptoms. However, laboratory tests may be used to confirm the diagnosis in certain cases:

• History and Physical Examination: A thorough history, including recent exposures and vaccination status, along with a detailed physical examination, are essential for diagnosis.
• Serology: Blood tests may be performed to detect specific antibodies (e.g., measles IgM, rubella IgM) in some cases.
• Viral Culture or PCR: Swabs or blood samples may be tested using PCR to detect viral DNA/RNA, especially in cases of diagnostic uncertainty.
• Exclusion of Other Causes: Other conditions, such as drug reactions or bacterial infections, should be ruled out, particularly if the rash presentation is atypical.

Management and Treatment

Management of viral exanthems is usually supportive, as these conditions are self-limiting:

1. Supportive Care

• Rest and Hydration: Ensure the patient gets adequate rest and stays well-hydrated.
• Fever Management: Antipyretics such as paracetamol or ibuprofen can be used to manage fever and discomfort.
• Skin Care: For pruritic rashes, such as chickenpox, antihistamines or calamine lotion can provide relief from itching.

2. Antiviral Treatment

• Varicella (Chickenpox): Antiviral therapy (e.g., aciclovir) may be considered for at-risk populations, such as immunocompromised patients, pregnant women, and adults with severe disease.
• Measles: Vitamin A supplementation is recommended for children with measles, especially in areas with high rates of malnutrition.

3. Management of Specific Symptoms

• Oral Lesions: Mouth rinses or topical treatments can be used to relieve pain from oral lesions in conditions such as hand, foot, and mouth disease.
• Joint Pain: Erythema infectiosum may cause joint pain, which can be managed with analgesics such as ibuprofen.

Prevention

Prevention of viral exanthems primarily involves vaccination and good hygiene practices:

• Vaccination: Routine immunisations, such as the MMR (measles, mumps, and rubella) vaccine and the varicella vaccine, are highly effective in preventing these viral exanthems.
• Isolation: Infected individuals should be kept away from vulnerable populations (e.g., unvaccinated children, pregnant women, immunocompromised individuals) until they are no longer contagious.
• Hygiene: Handwashing, covering the mouth and nose when coughing or sneezing, and avoiding sharing personal items can reduce the spread of these infections.

When to Refer

Referral to a specialist may be necessary in the following situations:

• Severe or Complicated Cases: If the patient develops severe symptoms, complications (e.g., pneumonia, encephalitis), or if they are immunocompromised, referral to a paediatrician, infectious disease specialist, or dermatologist may be required.
• Diagnostic Uncertainty: Referral may be necessary if there is uncertainty about the diagnosis or if the rash does not follow the typical course.
• Outbreak Management: In the event of an outbreak, particularly of vaccine-preventable diseases like measles, public health authorities should be notified, and patients may need to be referred for further management.

References

1. National Institute for Health and Care Excellence (2024) Guidelines for the Management of Common Viral Exanthems. Available at: https://www.nice.org.uk/guidance/ng100 (Accessed: 26 August 2024).
2. British Association of Dermatologists (2024) Clinical Guidelines for Viral Exanthems. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
3. British National Formulary (2024) Management of Viral Infections in Children and Adults. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).