Viral Exanthems

• Core 1 (Pre-Clerkship)
  • Biomedical Science
    • Microbiology I
      • Gram Positives Part 1: Intro and Streptococci
        • Newborn infections, scarlet fever
      • Gram Positives Part 2: Staphylococci
        • Toxin-mediated diseases including SSSS, TSS
      • Parasitology
        • TORCH infections
      • Vector-borne diseases
        • Lyme, RMSF
      • Herpesvirus
        • HSV 1 and 2, VZV, CMV
      • Childhood Viral Infections
        • Measles, rubella, parvovirus
    • Microbiology II
      • Infection Syndromes
        • Infections originating in the skin, viral exanthems, infection-related rashes
      • Viruses/Anti-virals
        • Perinatally acquired infections
  • Integrative Systems
    • Dermatology
      • Intro to Dermr
      • Skin of Color
      • Infestations
      • Fungal diseases
      • Bacterial diseases
      • HSV, VZV, and enterovirus,
      • Syphilis
      • Pediatric derm
      • Viral exanthems
• Core 2 (Clerkship)
  • Pediatric Clerkship Didactics on Fevers
• Core 3 (Post-Clerkship)
  • Electives that may further knowledge: Pediatric dermatology elective, Dermatology elective

A 2-year-old boy presents to the outpatient clinic with a history of fever and rash. 

His parents report that 3 days ago, he began experiencing a high fever (up to 104°F) and malaise, which lasted for 4 days. After the fever subsided, a generalized non-pruritic rash appeared, initially on his trunk and then spread to his extremities. The rash is described as erythematous and maculopapular. The child has been otherwise well-appearing throughout the course of his illness, with no significant respiratory or gastrointestinal symptoms. 

Onset, Duration, Location, and Progression:

• When did the rash first appear?
• What parts of the body did the rash initially affect?
• How has the rash spread since onset? (e.g., face to trunk to extremities, or localized to one area)
• Was the rash sudden or gradual in onset?
• Is the rash stable, or is it continuing to spread?

Appearance:

• What does the rash look like? (e.g., maculopapular, vesicular, pustular, petechial, urticarial)
• Has the rash changed over time? (e.g., any new features like blistering, peeling, or scaling?)
• Has the color or texture of the rash changed?
• Are there any ulcers, vesicles, or scabs?
• Is there any associated redness or swelling of the surrounding skin?

Associated Symptoms/Review of Systems:

• General: fever, chills, malaise?
• HEENT: conjunctivitis, visual disturbances, rhinorrhea, congestion, ear pain, sore throat
• Respiratory: cough, shortness of breath, wheezing?
• Cardiovascular: chest pain, lower extremity swelling, palpitations?
• Gastrointestinal: vomiting, diarrhea, abdominal pain?
• Neurologic: headache, neck stiffness, photophobia, seizures?
• Musculoskeletal: joint pain, muscle aches?

Exposure History:

• Any recent viral or bacterial infections prior to the rash (e.g., respiratory infections, gastrointestinal infections)?
• Any history of antibiotic use or other treatments that might alter the skin or immune response (e.g., antibiotics that could cause a rash)?
• Any close contact with someone who has been sick, particularly someone with a rash or an infectious disease?
• Any recent travel history (international or domestic), especially to regions where infectious diseases are endemic?
• Does the child attend daycare or school? Any outbreaks or sick children in these settings?
• Any recent contact with animals (domestic pets or livestock)?
• Any recent vector exposures (e.g., mosquito, tick bites)?

Past Medical History:

• Any chronic medical conditions (e.g., asthma, sickle cell disease, eczema)?
• Any history of immunosuppression (e.g, prolonged steroid use, HIV infection, solid organ transplant, rheumatologic diseases on TNF antagonists)?

Vaccination History:

• Up-to-date on childhood vaccinations (e.g., MMR, varicella, DTaP)?
• Any recent exposure to vaccine-preventable illnesses?
• Received seasonal influenza and/or COVID-19 vaccinations?

Social History:

• Is there anyone in the household or close contacts (siblings, parents) who is also ill or has a similar rash?
• Any living conditions (e.g., overcrowded housing, homelessness) that could affect exposure to infections or vectors?
• Is there exposure to environmental pollutants or known toxins?

General Assessment:

• Vital signs: Document abnormal vital signs (e.g., fever, tachycardia, tachypnea) and trend fever curve.
• Sick versus not sick: This is a key initial assessment. Children with life-threatening infections (e.g., meningococcal disease, toxic shock syndrome) will often appear ill and in distress.

Dermatologic Exam:

• Distribution of Rash
  • Face, Trunk, and Extremities:
    • Measles (Rubeola): Starts behind the ears or on the face, spreading downward to the trunk, arms, and legs.
    • Roseola: Often starts on the trunk and spreads to the face and limbs after fever resolves.
    • Varicella (Chickenpox): Rash starts on the face and trunk, often with lesions in various stages.
    • Erythema Infectiosum (Fifth Disease): Slapped cheek appearance, followed by a lacy or reticular rash on the trunk and limbs.
  • Lesion Characteristics:
    • Maculopapular: Flat red spots (macules) or raised spots (papules). Common in viral rashes like measles and rubella.
    • Vesicular Lesions: Small fluid-filled blisters, often seen in varicella (chickenpox), herpes simplex, or hand, foot, and mouth disease.
    • Pustular Lesions: Lesions filled with pus, as seen in impetigo (caused by Staph aureus or Strep pyogenes)
    • Petechial or Purpuric Lesions: Can indicate serious bacterial infections like meningococcal infection or Rocky Mountain spotted fever. Petechiae do not blanch with pressure.

Additional Exam Findings:

• HEENT (Head, Eyes, Ears, Nose, and Throat):
  • Mucous Membranes and Conjunctivae:
    • Conjunctivitis: Can be seen in measles (along with coryza and cough) and rubella.
    • Koplik Spots: Small, white spots inside the cheeks, characteristic of measles.
    • Oral Lesions: For herpes simplex virus (HSV), check for oral vesicles and ulcers. Hand, foot, and mouth disease may present with oral ulcers and vesicles on the mucous membranes.
  • Pharyngeal Exudate: Often seen in scarlet fever due to group A streptococcus infection.
• Lymphadenopathy:
  • Generalized vs. Localized
• GI (Gastrointestinal Exam):
  • Hepatomegaly or Splenomegaly: May indicate systemic viral infections such as mononucleosis (Epstein-Barr virus), cytomegalovirus, or parvovirus B19.
• Musculoskeletal (MSK) Exam:
  • Joint Involvement: Some viral infections can affect joints. For example:
    • Rubella can cause arthralgia and mild joint swelling, especially in adolescents.
    • Parvovirus B19 (Fifth disease) can lead to arthritis or arthralgia in older children or adults.
    • Joint involvement can also be seen in infectious arthritis (e.g., disseminated gonococcal infection).
  • Neurological Exam:
    • Focal Neurologic Deficits: May suggest encephalitis (associated with herpes simplex virus), meningitis (e.g., meningococcal disease), or encephalomyelitis seen in some viral infections (e.g., measles).
    • Seizures: Children with roseola may have a febrile seizure before the rash appears. Seizures may also be seen with more serious viral infections like herpes simplex encephalitis or varicella.
    • Meningismus: A sign of meningitis (e.g., meningococcal meningitis), including signs such as nuchal rigidity (neck stiffness), headache, and photophobia.

Here are some of the most common viral exanthems of childhood:

It is important to evaluate for other causes of infectious exanthems including bacterial (e.g., scarlet fever, impetigo), fungal (e.g., tinea infections), and parasitic/vector-borne (e.g., Lyme disease, Rocky Mountain spotted fever) infections.

• If the clinical diagnosis is unclear after thorough history and physical exam, lab tests may be needed to confirm the diagnosis and/or rule-out alternative diagnoses:
  • Skin swab: Polymerase Chain Reaction (PCR) for viral pathogens (e.g., varicella, herpes simplex) or Gram stain/bacterial culture for bacterial pathogens (e.g., staph aureus).
  • Throat culture or rapid antigen test for strep (scarlet fever).
  • Serum IgM/IgG antibodies for specific viruses if indicated.
  • Complete blood count (CBC) to check for leukocytosis, leukopenia, or thrombocytopenia.
• Once the differential diagnosis is narrowed, treatment can be initiated based on the specific condition:
  • Supportive care (e.g., for roseola, fifth disease).
  • Antiviral therapy for certain viral infections (e.g., acyclovir for herpes simplex).
  • Antibiotics for bacterial infections (e.g., penicillin for scarlet fever, mupirocin for impetigo).
  • Topical and/or oral antifungals for tinea infections.
  • Symptomatic treatment for fever and pruritus (e.g., acetaminophen, NSAIDs, anti-histamines).

• Most viral exanthems can be diagnosed using a thorough history and physical exam. Don’t forget to ask about vaccinations and exposure history (e.g., recent travel, sick contacts, animal contact/vector exposures)!
• The timing of rash appearance in relation to fever is often a strong diagnostic clue. For example, roseola typically presents with a high fever lasting 3-5 days, followed by a maculopapular rash that appears only after the fever resolves. This is one of the few exanthems where the rash appears after the fever.
• Some infectious rashes can be associated with serious complications, so it’s important to first assess whether the child is sick or not sick.

• Article
  • AAP Textbook of Pediatric Care: Contagious Exanthanemous Diseases
  • American Family Physician: Common Skin Rashes in Children
• Video
  • Osmosis: Viral Exanthems of Childhood
• Podcast
  • Peds Cases: Viral Rashes in Children
• Pathways
  • Suspected Measles Exposure or Infection (CHOP)

Answers:

Q1: a. Immediate isolation from others to prevent transmission

The child likely has measles, a highly contagious viral disease. It is critical to isolate the child to prevent transmission to others, particularly those who are immunocompromised or those who are not vaccinated. Measles is contagious from 4 days before to 4 days after the onset of the rash, and isolation should be strictly enforced during this period.

Incorrect Answers:

b. Administration of IV antibiotics

Measles is caused by a virus, and antibiotics are not effective. Antibiotics would only be used if there is a secondary bacterial infection.

c. Begin oral corticosteroids for rash control

Corticosteroids are not used for measles, as they can worsen the disease and increase the risk of secondary infections. The treatment is supportive, with a focus on symptomatic care.

d. Administration of live-attenuated vaccine

 The measles vaccine is preventive and should ideally be administered before exposure (or post-exposure to susceptible individuals in specific cases), but it is not indicated in acute disease.

Q2: a. Acyclovir

The child has varicella (chickenpox), and acyclovir is the first-line treatment for children who are immunocompromised or at risk for severe complications. Early treatment with acyclovir can decrease the severity and duration of symptoms. It can also reduce the risk of complications such as bacterial superinfection, pneumonia, and encephalitis.

Incorrect Answers:

b. Intravenous immunoglobulin (IVIG)

 IVIG may be used for immunocompromised patients with varicella to prevent severe disease, but acyclovir remains the first-line antiviral therapy.

 c. Penicillin

Penicillin is not effective against viral infections like varicella. It is only used for secondary bacterial infections that might develop later.

 d. Topical corticosteroids

 Topical corticosteroids are not recommended for varicella, as they can worsen the condition and increase the risk of secondary bacterial infection.

• Basic Dermatology: Viral Exanthems (Cases and Questions) (American Academy of Dermatology)