Erythematous rashes in children are common, with a long list of differential diagnoses from minor conditions to the potentially life threatening.
A general assessment should be made as to how sick the child is and vital signs should be checked. Red flag signs include an unusually high fever, tachycardia, tachypnoea, listlessness and delayed capillary refill or low BP. A child in the early stages of meningococcal septicaemia may have a blanching erythematous rash.
Scarlet fever is due to infection with a group A beta-haemolytic streptococci that produces an erythrogenic toxin. It occurs mostly in children aged four to eight years and by 10 years most children will be immune.
The illness starts with a fever, sore throat, headache and malaise. After 12-24 hours, an erythematous, blanching rash spreads over the body.
The perioral area is spared and the rash is often more marked in the skin folds. Desquamation may affect the palms and soles after two to four days.
Examination reveals tonsillitis with exudate and cervical lymphadenopathy, and usually a white-coated tongue with projecting pink papillae - the 'strawberry tongue' of scarlet fever. Treatment is with penicillin V for 10 days.
Resolution of skin changes may take a few weeks. Scarlet fever is usually benign, but without treatment can lead to complications including rheumatic fever, glomerulonephritis, osteomyelitis and pneumonia, as occurred frequently in the pre-antibiotic era.
In recent years, this viral infection has increased due to reduced uptake of the MMR vaccine.
In the UK, 80 per cent of measles cases are in children. At-risk groups include unvaccinated adults and infants, those who have only had one vaccine and the immunocompromised.
After a prodromal phase of fever, coryza, cough, malaise and conjunctivitis, the pathogonomic Koplik's spots appear, consisting of bright red spots with a blue-white centre on the buccal mucosa opposite the second molar.
The next phase is a high fever and an erythematous, blanching, maculopapular rash that starts behind the ears and spreads over the entire body within 24 hours. The rash may become confluent, especially on the face, and as it fades it leaves brown coppery lesions with scale.
Measles is a notifiable disease, and the local public health team may advise swabs or serum samples to confirm the diagnosis.
Treatment is supportive, but as many as 30 per cent of cases have one or more complications, including severe diarrhoea, otitis media, pneumonia and encephalitis.
Slapped cheek disease
Slapped cheek disease, also known as fifth disease or erythema infectiosum, is caused by the B19 parvovirus.
Transmission is by respir-atory secretions, commonly affecting school age children. Thirty per cent of those affected are asymptomatic.
The illness begins with firm, red, burning hot cheeks. One to four days later a lacy reticular rash appears on the body. The child is usually otherwise quite well with just a mild fever and headache. Arthralgia and abdominal pain may rarely occur.
Treatment is supportive, and the main complications are aplastic crisis in patients with blood disorders, and miscarriage, intrauterine death or hydrops fetalis in pregnancy.
If fifth disease is diagnosed in a close contact of someone who is pregnant or in a pregnant mother, specialist advice should be sought. Serial blood tests are usually advised, and if maternal infection is confirmed, repeated ultrasounds are needed to assess fetal growth to detect hydrops fetalis. The risk is greater in the first 20 weeks, and there is no evidence of an increase in fetal abnormalities.
Roseola infantum is due to herpes virus type-6, and is most common in children aged six to 18 months. It is rare in adults as infection confers lifelong immunity.
Typically, the child will have had a fever and mild pharyngitis for three or four days, and the rash appears as the fever subsides. A maculopapular rash of non-itchy small pink blanching spots, often with a white halo, starts on the trunk and spreads to the face and extremities.
Roseola infantum resolves over two days without desquamation or pigmentation. Treatment is supportive. Febrile convulsions are the most common complication in about 10 per cent of affected children.
Scalded skin syndrome
Staphylococcal scalded skin syndrome (SSSS) is caused by epidermolytic toxins from toxigenic strains of Staphylococcus aurous. It most commonly affects children under five years, particularly neonates.
Outbreaks are often seen in nurseries and childcare facilities. Foci of infection for SSSS include purulent conjunctivitis, otitis media and occult nasopharyngeal infection.
It starts with a fever, irritability, widespread erythema and characteristic tissue paper-like wrinkling of the epidermis. Fluid-filled blisters develop within 24 hours that easily rupture and leave areas that are moist, red and tender and look like burns. Blisters tend to affect the groin and axillae initially, then spread to other areas.
Children with suspected SSSS should be referred to hospital for IV antibiotics. Although the appearance is severe, children usually make a complete recovery within a week of starting antibiotics. Possible complications include septicaemia, cellulitis and pneumonia.
While infections are by far the most common causes of erythematous rashes in children, GPs must remember that some non-infectious conditions such as Kawasaki disease, erythema nodosum and erythema multiforme can occur in the newborn.
- Dr Mistry is a GP in north-west London.
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