Unilateral laterothoracic exanthem 1_0412 Derm Dx
Unilateral laterothoracic exanthem 2_0412 Derm Dx
Unilateral laterothoracic exanthem 3_0412 Derm Dx
Unilateral laterothoracic exanthem 4_0412 Derm Dx
A 5-year-old boy presents to the dermatology clinic with a rash around his left armpit, left torso and left upper arm that his mother reports has been present for seven days.
The patient had surgery several weeks prior to rash onset, which consisted of an incision on the left upper trunk to place a nerve stimulator. During surgery, the patient’s skin was cleansed with a chlorhexidine scrub.
A few days prior to rash onset, the mother recalls the patient had a very mild cold. He denies fever, but endorses mild pruritis. There is no history of sick contacts.
On exam, the boy is afebrile, well nourished, well developed and appears nontoxic. A full-body skin exam is significant for pink macules and papules around the left axilla, extending to the left lateral trunk and left arm. The prior surgical incision is clean, dry and intact. What’s your diagosis?
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This patient has unilateral laterothoracic exanthema (ULE). ULE is a unique exanthem of unknown etiology, but most clinicians ascribe it to a mild viral infection. It occurs most commonly in winter and spring in children aged 1 to 5 years.
In most patients, the eruption is unilateral and located on the trunk in a peri-axillary distribution. It may spread in a centrifugal fashion and become bilateral, but the eruption will still predominate on the initial side. About 50% or more of patients complain of mild pruritis. At least two-thirds of patients complain of a mild upper respiratory or gastrointestinal infection preceding the eruption.
Diagnosis is clinical, but a biopsy may be performed if it is in doubt. Although this patient’s history may suggest a contact dermatitis to the surgical scrub, the morphology of these lesions is much more consistent with an exanthemous process than a contact dermatitis.
Additionally, allergic contact dermatitis is generally very pruritic, such as with poison ivy — the prototypical allergic contact dermatitis.
Treatment and prognosis
Treatment is supportive. Topical steroids help minimally. The rash will resolve spontaneously within three to six weeks.
Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.
1. Bolognia J, Jorizzo JL, Rapini RL. “Chapter 80: Other Viral Diseases.” Dermatology. St. Louis, Mo.: Mosby/Elsevier, 2008.
2. James WD, Berger TG, Elston DM et al. “Chapter 19: Viral Diseases.” Andrews’ Diseases of the Skin: Clinical Dermatology. Philadelphia: Saunders Elsevier, 2006.