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Author: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1999. Updated in September 2015.
Laterothoracic exanthem is an uncommon rash affecting young children, which is suspected to be triggered by a viral infection.
Laterothoracic exanthem is also known as Asymmetric Periflexural Exanthem of Childhood (APEC). A new name has been proposed: superimposed lateralised exanthem of childhood (2014).
Laterothoracic exanthem affects twice as many girls as boys. The average age is two, most cases being between one and five years old.
From time to time, a specific virus has been associated with laterothoracic exanthem. Following observing a case associated with adenovirus reported in 2014, authors speculated that early postzygotic mutation has rendered the skin on one side of the body more reactive to an infective agent. Subsequent involvement of the other side of the reflects less reactive skin on that side.
Laterothoracic exanthem mainly occurs in winter and spring, as is common for viral infections. It has been specifically associated with Epstein-Barr virus, adenovirus and parvovirus B19.
The rash is often mistaken for eczema (dermatitis) or a fungal infection (ringworm). It usually starts in the armpit or groin and gradually extends outwards, remaining predominantly on one side of the body. It may spread to the face, genitalia, hands or feet.
Laterothoracic exanthem starts as tiny raised pink papules, which may be surrounded by a pale halo. These become flat and scaly over the next week or two. The middle of older patches fades to a dusky grey. Occasionally the patches are net-like or in rings. Little blisters or blood spots may occur. The rash is usually quite itchy.
Sometimes other features of viral infection occur at the onset of the rash, such as a fever, sore throat, cold, vomiting and/or diarrhoea. The lymph glands in the armpits and groins may be enlarged.
The rash lasts for several weeks, but always resolves spontaneously within three months.
Laterothoracic exanthem clears without treatment. The itching can be relieved with:
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