What is an exanthem?
Exanthem is the medical name given to a widespread rash that is usually accompanied by systemic symptoms such as fever, malaise and headache. It is usually caused by an infectious condition such as a virus, and represents either a reaction to a toxin produced by the organism, damage to the skin by the organism, or an immune response.
What causes exanthems?
Exanthems during childhood are very common and are usually due to specific viral infections:
- Chickenpox (varicella)
- Measles (morbillivirus)
- Rubella (rubella virus)
- Roseola (herpes virus 6B)
- Erythema infectiosum (parvovirus B19).
Viral exanthems also include:
- Acute human immunodeficiency virus infection syndrome
- Viral hepatitis
- Infectious mononucleosis and aminopenicillin rash (Epstein Barr virus)
- Papular purpuric glove and socks syndrome (parvovirus B19)
- Pityriasis rosea (herpes virus 6 and 7)
- Papular acrodermatitis of childhood
- Erythema multiforme
- Unilateral laterothoracic exanthem
- Some cases of acute generalised exanthematous pustulosis
- Nonspecific viral exanthem.
Exanthems caused by bacterial infections include:
- Staphylococcal toxin infections
- Streptococcal toxin infections
- Kawasaki disease.
Other specific infections that can give rise to exanthems include:
Acute connective tissue diseases can present with an exanthem.
What are the signs and symptoms of exanthems?
Non-specific exanthems appear as spots or blotches and may or may not be itchy. The rash is usually widespread and may be more extensive on the trunk than the extremities. In most cases, prior to the rash appearing, patients may have symptoms of general unwellness that include:
- Loss of appetite
- Abdominal pain
- Muscular aches and pains.
These signs and symptoms may vary depending on the cause of the exanthem. See individual causes for details. Viral exanthems often occur in small epidemics, so there may be other children effected at the same time.
Diagnosis of exanthems
Many exanthems have distinct patterns of rashes and prodromal (pre-rash) symptoms allowing clinical diagnosis.
Consult local laboratory resources to determine the most suitable tests in case of doubt, particularly in a very sick patient or if the exanthem arises during pregnancy or immune suppression.
Tests may include:
- Viral swab for viral culture, immunofluorescence and PCR
- Blood tests for serology, PCR, RNA/DNA, ANA and tissue antibodies
What is the treatment for exanthems?
Treatment of specific exanthems will depend on the cause.
Symptomatic treatment may include:
- Paracetamol to reduce fever
- Moisturising emollients to reduce itch.