Viral Childhood Exanthems
Viral rashes are often caused by
immune reactions to the virus and cell damage caused by the virus.
A key bacterial cause of rash is
Streptococcus pyogenes, which causes Scarlet Fever.
Helpful distinguishers between the viral exanthems:
Initial location and pattern of the rash.
Three viral exanthems tend to initiate on the face:
Measles, rubella, and erythema infectiosum.
Face/Scalp & Trunk:
Chickenpox
Trunk:
Roseola infantum typically first appears on the trunk
Hand, Foot, and Mouth disease produces rash on the hands and feet, in the mouth.
Be aware that these are meant to be helpful generalizations, and may not always hold true; for example, hand, foot, and mouth disease can also produce rash on the buttocks.
Multiple rash types can exist at once.
Macules are flat, colored spots on the skin.
Papules are solid, raised areas; larger papules are called nodules.
Vesicular rashes comprise raised "pockets" of fluid in the skin.
Timing of Rash/Other Signs and Symptoms:
The timing of the rash and presence of other symptoms can also help distinguish among the exanthems.
For example, some infections are associated with fever, malaise, and respiratory symptoms.
Knowing the time lapse between virus introduction and symptom appearance can also help, although the incubation periods of the various viruses often overlap and may include a wide range.
Hand, foot, and mouth disease
Usually caused by
Coxsackievirus A.
Average incubation period of 3-6 days.
Most common in children younger than 5.
As its name suggests, hand, foot, and mouth disease is characterized by a rash that can be macular, maculopapular, or vesicular on the hands, feet, and in and around the mouth.
Erythema infectiousum, aka, Fifth Disease
Caused by
Parvovirus B19.
Average incubation period of 7 days.
Tends to affect children 5-15 years old.
Initial symptoms can include fever, runny nose, headache; diarrhea is also possible.
These flu-like symtpoms are followed by a malar facial rash that spreads to the trunk and extremities.
Facial rash takes on a characteristic "slapped cheeks" pattern, whereas the rash on the extremities often comprises maculopapular rash in a "lacy" pattern.
Roseola infantum, aka, exanthema subitum
Most commonly caused by
Human Herpes Virus 6, and sometimes Human Herpes Virus 7.
Roseola infantum is also sometimes called "6th disease", because it was the 6th exanthema identified (erythema infectiosum was the fifth).
Average incubation period is 9 days.
Although disease can occur in a wide range of ages, it most commonly affects children younger than 2 years old.
Initial symptoms include a very high fever (exceeding 104 degrees Fahrenheit/40 degrees Celsius).
The fever lasts approximately 3 days, which is why Roseola infantum is sometimes called "3-Day Fever".
Macular or maculopapular "blanching rash" arises first on the trunk.
"Blanching rash" means that when the skin is pressed upon, often with a clear glass, the rash fades from red to pale.
Another common finding are red uvulopalatoglossal spots, aka, Nagayama spots.
A range of other symptoms, including gastrointestinal, respiratory, ocular, and auditory problems, can occur.
Febrile seizures are a common complication in roseola infantum.
Caused by
Varicella-Zoster virus (aka, Human Herpes Virus-3)
Average incubation period is 16 days.
Often affects children younger than 5.
Prior to rash, patients may experience fever, malaise, sore throat, and low appetite.
Rash is characterized by crops of lesions that pass through macular, vesicular, and crusted phases.
– Lesions usually first appear on the head/neck, and spread to the rest of the body.
Clinical correlation:
Shingles is an illness that occurs in adults upon reactivation of the Varicella-Zoster Virus; the reactivated virus is called Herpes-Zoster Virus.
Whereas the chickenpox rash is often itchy, the shingles rash can be very painful. Vaccination against Varicella-Zoster virus also prevents shingles.
Caused by the
Measles virus.
Average incubation period is 14 days.
Prior to rash, patients often experience Fever and the "Three C's": Cough, Coryza (runny nose), and Conjunctivitis.
These symptoms are followed by a maculopapular rash that begins on the face and neck and spreads.
Before the body rash, many patients also develop
Koplik spots, which are spots along the palate and internal buccal surfaces (these spots are sometimes calked Koplik's sign).
Serious complications from measles virus infection include potentially fatal pneumonia and encephalitis; vaccination helps to prevent these and other complications.
Rubella (aka, German measles)
Caused by
Rubella virus.
Average incubation period is 14 days.
Rubella is characterized by the acute onset of a pink maculopapular rash that begins on the face and spreads.
The rash lasts about 3 days, so Rubella is sometimes called "3-Day measles" – careful not to confuse this with
Roseola infantum, which is sometimes called "3-Day Fever."
Some patients also have swollen lymph nodes in the neck area; systemic symptoms, such as headache, are mild if present.
Congenital rubella, which is contracted during fetal development, is associated with severe birth defects; this form of rubella can also be prevented by the rubella vaccine.
