Unilateral laterothoracic exanthem. A clinicopathologic study of forty-eight patients

Four years ago, we began seeing young children with an unusual, predominantly unilateral, morbilliform and eczematous, self-limited cutaneous eruption. It appeared to correspond to unilateral laterothoracic exanthem (ULE) reported from France and to an eruption described as "a new papular erythema of childhood" in the United States.

We conducted a prospective study of ULE to define its clinical evolution, pathology, and therapy. In addition, we performed epidemiologic and microbiologic investigations in an attempt to determine the cause of ULE.

We studied 48 children with ULE. In some patients, blood, urine, stool, as well as skin biopsy specimens were analyzed.

ULE is a morbilliform, eczematous eruption that often begins close to the axilla and spreads to become bilateral, although it usually retains a unilateral predominance. Patients' mean age at onset is 24.3 months, with a female predominance (2:1) and mean duration of 5 weeks, followed by spontaneous resolution that may or may not be improved with topical corticosteroids. It is characterized by a unique eccrine lymphocytic infiltration. Although signs of infection were reported by most patients, no one infectious agent was identified. No significant epidemiologic factor was found.

ULE, in young children, is a self-limited morbilliform and scarlatiniform eruption that may represent a specific skin reaction to one or more infectious agents.