Erythematous rashes in children are common. This review focuses on infectious causes and important differential diagnoses.
When evaluating children with a rash, several features should be considered (see table 1).
|Table 1: Evaluation of rash in a child|
|Associated symptoms||Morphology of lesions|
|Current and previous medications||Distribution pattern|
|Existing systemic conditions||Duration of lesions|
|Exposure to infection||Physical examination, including oral lesions|
|Social and recreational activities|
Rash can be maculopapular, pustular, vesiculobullous, diffuse erythematous, or petechial/purpuric in nature. Different types can co-exist or evolve from one to another. Associated systemic features include pyrexia, pruritus, lymphadenopathy and hepatosplenomegaly.
Red flag signs are high fever (>38.5oC), tachycardia, tachypnoea, reduced level of consciousness, delayed capillary refill and hypotension. It is important to exclude conditions requiring prompt intervention such as meningococcal septicaemia.
Several viral and bacterial illnesses are accompanied by localised or generalised skin eruptions called exanthems. The rash may be the first manifestation and most common reason for parents or patients to seek medical attention. Some viruses cause well recognised distinct eruptions, while others are non-specific.
Measles, caused by the highly contagious Paramyxovirus, spreads by respiratory droplet and occasionally by the conjunctival route. The incubation period is 10-14 days. Classic presentation is with fever and the three Cs - cough, coryza, and non-purulent conjunctivitis.
The pathognomonic enanthem, ‘Koplik spots’, present in the prodrome as punctuate, grey-white spots with an erythematous halo on the buccal mucosa opposite molar teeth (grains of salt). The skin eruption follows 2–4 days later on the face and spreads downwards to the trunk and extremities.
Lesions are erythematous to purple-red macules and papules, which may become confluent and fade in the same order as their appearance, leaving coppery macules and desquamation. Complications include pneumonia, bronchitis, otitis, gastroenteritis, myocarditis, and encephalitis.
Rubella (German measles)
Rubella, a Togaviridae RNA virus, spreads by the respiratory route and has an incubation period of 12-23 days. Young children may not have a prodrome. Pink macules and sometimes papules start on the face and spread caudally, are fainter than measles lesions and do not coalesce. They tend to fade after 1-3 days.
Lymphadenopathy is common, especially postauricular and occipital nodes. Forscheimer’s spots, petechiae over the soft palate and uvula, occur just before or with the exanthem.
Erythema infectiosum (fifth disease, slapped cheek disease)
Erythema infectiosum is caused by parvovirus B19 and spreads mainly by respiratory infection. About 30% of cases are asymptomatic. Characteristic fiery-red facial erythema occurs 2-3 days following prodromal symptoms, followed by lacy, reticulated eruptions which may be pruritic on the extremities and trunk.
Aplastic crisis is the main complication, with miscarriage, intrauterine death or hydrops fetalis in pregnancy. Specialist advice is needed in these cases.
Roseola infantum (sixth disease/exanthem subitum)
Caused by herpes virus type-6, roseola infantum is most common in children aged 6-18 months and is transmitted through saliva. The classic presentation is high fever for 3–5 days.
As the temperature normalises, erythematous macules and papules appear on the trunk and spread to the extremities, neck, and face. These resolve over 1–3 days. Febrile convulsions occur in around 10 per cent of cases.
Chicken pox (varicella zoster)
Spread by aerosol or blister fluid contact, the incubation period is 2-3 weeks. A prodrome of fever, malaise, headache and myalgias may occur. A hairline rash typically spreads caudally to the extremities and trunk which has the highest number of lesions, so there is a centripetal distribution.
Classic lesions are described as ‘dewdrops on a rose petal’, that is a red macule developing into a papule, a vesicle with an erythematous halo and crust over 3-4 days, giving skin lesions at different stages. Aciclovir is given to immunocompromised children.
Hand foot and mouth disease (HFMD)
HFMD is caused by coxsackievirus A16 infection. It is highly contagious and is spread by the faecal-oral route, contact with skin lesions, and oral secretions. Sore throat and dysphagia tend to be the presenting symptoms.
Ulcers on an erythematous base affect the tongue, buccal mucosa and occasionally the palate, gums and lips. In 70-80% of children, lesions occur on the hands and feet (palmoplantar) and occasionally the buttocks. Lesions may vesiculate and crust, resolving over 7-10 days.
Staphylococcal scalded skin syndrome (SSSS)
Staphylococcal scalded skin syndrome typically occurs in children less than four years of age due to exotoxins produced by Staphylococcus aureus.
Clinical features include fever, irritability, skin tenderness and scarlatiniform erythema with accentuation in flexural areas. Within 24-48 hours, flaccid sterile blisters and very superficial erosions develop and swabs show no growth.
Treatment is with intravenous antibiotics, commonly flucloxacillin. Differential diagnosis includes toxic epidermal necrolysis which has mucosal involvement.
Toxic shock skin syndrome (TSS)
The symptoms of toxic shock syndrome are high fever, diffuse erythematous rash, hypotension and involvement of three or more organ systems. TSS can be menstrual, associated with tampon use. Toxins (TSST-1) are produced by Staph. aureus.
A scarlatiniform eruption, often with flexural accentuation, is frequently present. Palm and sole erythema and oedema, conjunctival and mucous membrane hyperaemia and strawberry tongue often occur. Treatment is with intravenous antibiotics. Skin desquamation occurs 1–2 weeks after onset.
Scarlet fever is exotoxin mediated, and is caused by group A beta haemolytic Streptococci, commonly following pharyngitis or tonsillitis in children 1-10 years of age. Initially the tongue is white-coated with red oedematous papillae (white strawberry tongue). By 4-5 days, the coating peels off, leaving a red, glistening tongue with prominent papillae (red strawberry tongue).
The exanthem is fine and erythematous, with macules or papules described as ‘sandpapery’ involving the trunk and extremities, and it may have flexural accentuation with a petechial component (Pastia’s lines). It generally resolves over 4-5 days, but may leave hand and foot desquamation. Antistreptolysin (ASO) titre will be raised. Treatment is with penicillin or erythromycin.
Gianotti Crosti syndrome (Papular acrodermatitis of childhood or PAC)
Papular acrodermatitis of childhood occurs in children aged 1-6 years. Prior to the exanthem, upper respiratory symptoms, fever, and lymphadenopathy may occur.
Characteristic oedematous, erythematous, monomorphous papules or papulovesicles are symmetrically distributed on the face, buttocks and extensor surfaces of the limbs. The trunk is usually (but not always) spared. Mild pruritus may be present.
A number of viral infections can cause PAC including hepatitis A and C, herpesvirus 6, Epstein-Barr virus, cytomegalovirus, coxsackievirus and adenovirus. The eruption may last 8–12 weeks.
Drug-induced hypersensitivity syndrome
Drug induced hypersensitivity syndrome presents as a morbilliform (measles-like) eruption that involves the face, trunk, and arms, with later involvement of lower extremities. Symptoms typically occur 2-6 weeks after drug initiation.
Common drugs include anticonvulsants, sulphonamides, allopurinol and NSAIDs. Fever, lymphadenopathy, and clinical features of severe visceral involvement may occur. Criteria for diagnosis are: drug-induced generalised eruption, associated systemic involvement (lymph node or visceral), eosinophilia and/or circulating atypical lymphocytes.
The classic presentation of Kawasaki disease is an irritable child less than five years old with fever for five days plus four of the following: erythematous polymorphic rash, stomatitis (injected pharynx, strawberry tongue) and fissuring cheilitis, hand and foot oedema, conjunctival injection and cervical lymphadenitis.
An erythematous, desquamating perianal eruption may occur early in the first week. Desquamation of fingers and toes starts 1-2 weeks after the acute illness. Coronary artery aneurysms occur in 20-25% of untreated children. Therapy is with intravenous immunoglobulins (IVIG).
This is a mild inflammatory exanthem characterised by salmon-coloured oval macules and papules with a collarette of scale. A single initial herald patch may persist a week or longer before smaller lesions appear. Lesions last 3-8 weeks.
An urticarial eruption occurs within minutes to hours of exposure to an allergen. Each lesion lasts 24-48 hours, but there are recurrent crops. Symptoms include generalised swelling, airway compromise, hypotension, and tachycardia.
- Dr Dharshini Sathishkumar is clinical fellow in paediatric dermatology, Birmingham Children’s Hospital NHS Foundation Trust
- Dr Helen Goodyear is consultant paediatrician with a special interest in paediatric dermatology, Heart of England NHS Foundation Trust
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