In 1962, Brunner et al reported a "new papular erythema" in 75 children aged 6 months to 5 years.  Later, in 1992, Bodemer and de Prost published a case series of 18 children and named the condition unilateral laterothoracic exanthem (ULE).  In 1993, Taieb and colleagues suggested the term asymmetric periflexural exanthem of childhood (APEC) to replace ULE, as the latter did not fully depict the morphologic distribution of the skin lesions present in this condition.  Asymmetric periflexural exanthem of childhood is classified as a rare self-limited and spontaneously resolving exanthem with unknown etiology that occurs in children.  To date, only 3 case presentations in adults have been documented. [5, 6, 7]
The etiology of asymmetric periflexural exanthem of childhood is unknown. The patient's history (eg, age at presentation, multiple affected children in a family), lack of efficacy of broad-spectrum antibiotic treatment, serologic findings, and the tendency for presentation during spring and winter raise the possibility of a viral etiology. [8, 9, 10, 11] However, the evidence has been inconclusive, and clinicians have not been able to isolate a specific virus. Therefore, this hypothesis has never been confirmed.
Asymmetric periflexural exanthem of childhood manifests as an exanthem with stereotypical morphology and distribution. Biopsy is rarely if ever performed, as the presentation of this condition is unique and resolves spontaneously without treatment or adverse sequelae.
Asymmetric periflexural exanthem of childhood is a relatively rare condition that often appears in spring and winter months.
Approximately 300 cases have been reported in the literature. Case series of affected children have been documented internationally from the United States, Canada, and Europe.
Asymmetric periflexural exanthem of childhood predominantly affects individuals from light-skinned ethnic groups.
Asymmetric periflexural exanthem of childhood tends to affect females more frequently than males, with an estimated female-to-male ratio of 2:1.
The average age of presentation is 2 years, though affected children may be aged 4 months to 10 years. Four cases of asymmetric periflexural exanthem of childhood in adults have been reported in the literature.
The prognosis is excellent; the course of asymmetric periflexural exanthem of childhood is self-limited and spontaneously resolves in 4-6 weeks without medical intervention.
The unique presentation and appearance of skin lesions may be a cause of significant concern to the patient and his or her parents or caregivers. The patient should be educated and reassured that asymmetric periflexural exanthem of childhood a benign, self-limited exanthem without sequelae (eg, systemic symptoms, post-inflammatory hyperpigmentation, scarring, other skin changes).
For excellent patient education resources, visit eMedicineHealth's Skin, Hair, and Nails Center. Also, see eMedicineHealth's patient education articles Skin Rashes in Children and Swollen Lymph Nodes.
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