asymmetric periflexural exanthem


In 1962, Brunner et al reported a "new papular erythema" in 75 children aged 6 months to 5 years. [1Later, in 1992, Bodemer and de Prost published a case series of 18 children and named the condition unilateral laterothoracic exanthem (ULE). [2In 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. [3Asymmetric periflexural exanthem of childhood is classified as a rare self-limited and spontaneously resolving exanthem with unknown etiology that occurs in children. [4To date, only 3 case presentations in adults have been documented. [567]


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. [891011However, 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.


The exact cause of this eruption is unknown, and no specific viral pathogens have been identified.



United States
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.

Patient Education

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 patient education resources, visit the Skin, Hair, and Nails Center. Also, see the patient education articles Skin Rashes in Children and Swollen Lymph Nodes.


Most affected children are healthy and asymptomatic at presentation, with an unremarkable medical history. Occasionally, patients may report a current and/or recent episode of upper respiratory tract infection, adenopathy/lymphadenopathy, fever, otitis media, or diarrhea. In rare instances, other children in the family may also have asymmetric periflexural exanthem of childhood. Mild pruritus is reported in approximately 50% of patients.

Physical Examination

The primary (pathognomonic) lesion is a small erythematous papule with a surrounding pale halo. The general appearance of lesions includes a morbilliform, eczematous, and occasionally reticulated group of macules, papules, or coalescent plaques. These are occasionally accompanied with fine scaling.
At the initial onset, lesions are unilateral and usually begin near the axillae, lateral trunk, and upper inner arm or groin. During the course of the condition, lesions often progress bilaterally with an asymmetric predominance.
The 4 sequential stages of the lesions are as follows:
  1. Eczematous, when initial lesions occur on the axillae and lateral chest wall
  2. Coalescence, when lesions extend to the trunk and proximal extremities and are separated by areas of normal skin
  3. Regression, when older lesions may develop a central dusky-gray center
  4. Desquamation, when residual branlike scale appears and resolves with time
Asymmetric periflexural exanthem of childhood lesions spare the face, palms, soles, and mucous membranes. Lichenification is not usually observed. See the images below.
Morbilliformlike eruption in a child with involvemMorbilliformlike eruption in a child with involvement of the axilla, lateral thorax, and abdomen. Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.
Eczematouslike eruption with a predominantly hemicEczematouslike eruption with a predominantly hemicorporeal distribution photographed on the eighth day after initial appearance of lesions. Used with permission from Bodemer and de Prost (1992) from the Journal of the American Academy of Dermatology.
Pattern of reticulated plaques on the posterior loPattern of reticulated plaques on the posterior lower limb of a child. Used with permission from McCuaig et al (1996) from the Journal of the American Academy of Dermatology.

Differential Diagnoses


Medical Care

No specific medical treatment is required for asymmetric periflexural exanthem of childhood (APEC). Low-potency topical steroids may be used, though a minimal response is expected. Hydroxyzine may be used to alleviate pruritus. The use of moisturizers may be recommended to manage pruritus and fine scaling.

Medication Summary

The management of asymmetric periflexural exanthem of childhood typically does not require the use of prescription medications. Low-potency topical steroids such as hydrocortisone 0.5-1% may be used to control inflammation although it usually offers marginal benefit. Hydroxyzine may also be used if the lesions are pruritic and appear disruptive to daily functioning and interfere with normal sleep patterns.

H1-receptor antagonist antihistamines

Class Summary

These agents prevent the histamine response in sensory nerve endings and blood vessels but are not effective at reversing it. They competitively inhibit the binding of histamine at the H1 receptor. Histamine is responsible for mediating wheal and flare reactions, smooth muscle contraction, bronchial constriction, mucus secretion, edema, CNS depression, hypotension, and cardiac arrhythmias.

Hydroxyzine hydrochloride (Vistaril, Atarax, Vistazine)

Hydroxyzine hydrochloride antagonizes H1 receptors in the periphery. It may also suppress histamine activity in subcortical region of the CNS.

Topical anti-inflammatory agents

Class Summary

These agents provide relief of inflammatory eczematous lesions.

Hydrocortisone - topical (LactiCare-HC, Cortaid, Cortate)

Hydrocortisone is a low-potency topical corticosteroid with anti-inflammatory activity, as well as mineralocorticoid and glucocorticoid properties. It decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing increased capillary permeability. Use 1% cream.


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