What is erythema infectiosum?
Erythema infectiosum is a common childhood infection causing a slapped cheek appearance and a rash. It is also known as fifth disease and human erythrovirus infection.
What is the cause of erythema infectiosum?
Erythema infectiosum is caused by an erythrovirus, EVB19 or Parvovirus B19. It is a single-stranded DNA virus that targets red cells in the bone marrow. It spreads via respiratory droplets, and has an incubation period of 7–10 days.
Who gets erythema infectiosum?
Erythema infectiosum most commonly affects young children and often occurs in several members of the family or school class. Thirty percent of infected individuals have no symptoms. It can also affect adults that have not been previously exposed to the virus.
What are the symptoms of erythema infectiosum?
Parvovirus B19 infection causes nonspecific viral symptoms such as mild fever and headache at first. The rash, erythema infectiosum, appears a few days later with firm red cheeks, which feel burning hot. This lasts 2 to 4 days, and is followed by a pink rash on the limbs and sometimes the trunk. This develops a lace-like or network pattern.
Although most prominent in the first few days, the rash can persist for up to six weeks at least intermittently, and is most obvious when warm.
Complications of erythema infectiosum
Although usually a mild childhood condition, erythrovirus B19 infection can result in complications. These include:
- Polyarthropathy in infected adults (painful, swollen joints)
- Aplastic crisis or potentially dangerous low blood cell count in patients with haemolytic blood disorders such as autoimmune haemolytic anaemia and sickle cell disease
- Spontaneous abortion, intrauterine death (9%) or hydrops fetalis in 3% of the offspring of infected pregnant women. This can occur if erythema infectiosum occurs in the first half of pregnancy. Parvovirus B19 does not cause congenital malformations. As the risk of an adverse outcome is low, the infection is not routinely screened for in pregnancy
- Chronic parvovirus infection in immunodeficient patients, such as organ transplant recipients, causing erythropoietin-resistant anaemia, proteinuria, and glomerulosclerosis in a renal allograft
- Rarely, encephalitis, hepatitis, non-occlusive bowel infarction, amegakaryocytic thrombocytopenia, myositis and heart disease
How is the diagnosis of erythema infectiosum made?
In most cases, erythema infectiosum is a clinical diagnosis in a child with characteristic slapped cheek and lacy rash. Parvovirus can cause other rashes such as a papular purpuric gloves and socks syndrome. The diagnosis can be confirmed by blood tests.
- Parvovirus serology: IgG, IgM. This test is reported in about 7 days.
- Parvovirus PCR is more sensitive. This test is reported in about 3 days.
- In situ hybridisation or immunohistochemistry on biopsy specimens
If the child is unwell, or has haemolytic anaemia, a full blood count should be performed. Ultrasound examination and Doppler examination of at-risk pregancies can detect hydrops fetalis.
Treatment of erythema infectiosum
Erythema infectiosum is not generally a serious condition. There is no specific treatment. Affected children may remain at school, as the infectious stage or viraemia occurs before the rash is evident.
- The application of an ice-cold flannel can relieve the discomfort of burning hot cheeks.
- Red blood cell transfusions and immunoglobulin therapy can be successful in chronic parvovirus infection or during an aplastic crisis.
- Hydrops fetalis due to parvovirus infection is treated by intrauterine transfusion.