Continuing Education Activity

Asymmetric Periflexural Exanthem (APEC) is a distinctive and self-limited exanthem that classically affects children and, less frequently, adults. The precise etiology of this condition is unknown, but the hypothesis of a viral cause seems plausible but remains unconfirmed. APEC manifests as a unilateral papular exanthem with stereotypical morphology and distribution. Usually, laboratory investigations and biopsies are unnecessary for this condition because of its excellent prognosis and self-limited character in a few weeks. This activity describes APEC's evaluation, diagnosis, and management and highlights the role of team-based interprofessional care for affected patients.

Objectives:

• Identify the etiology of asymmetric periflexural exanthem.

• Determine the presentation of asymmetric periflexural exanthem.

• Assess the treatment and management options available for asymmetric periflexural exanthem.

• Communicate the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by asymmetric periflexural exanthem.

Introduction

Asymmetric periflexural exanthem of childhood (APEC) is a dermatosis described in 1962 by Brunner et al as "a new papular erythema.’’[1] In 1986, Taieb et al also described this disease and then suggested the term APEC in a second publication in 1993.[2] APEC is a distinctive and self-limited exanthem that classically affects children and, less frequently, adults.[3] The precise etiology of this condition is unknown, but the hypothesis of a viral cause seems plausible but remains unconfirmed. APEC manifests as a unilateral papular exanthem with stereotypical morphology and distribution. Usually, laboratory investigations and biopsies are unnecessary for this condition because of its excellent prognosis and self-limited character in a few weeks. 

Etiology

The etiology of this dermatosis remains unknown despite an active search for a causative agent. However, many factors favor viral origin, such as the involvement of several children in a single family, serologic findings, upper respiratory tract or digestive prodromes, antibiotic inefficiency, and epidemics in the spring.[3][4][5]Virologic examination seems to support this assumption. However, more than 1 virus appears capable of evoking the disease.

Duarte et al considered a relationship between infections with parainfluenza virus 2 or 3, adenovirus, human herpesvirus 6 or 7, and Epstein–Barr virus.[6]There is a report of asymmetric periflexural exanthem of childhood in a 3-year-old girl following an upper respiratory tract infection and the onset of axonal Guillain-Barré syndrome.[3] Parvovirus B19 has been reported as a viral infection associated with APEC in 2 female children and 1 adult patient.[4][7]

Other possible causes of APEC merited consideration by various authors, including insect bites, bacterial infections, and contact dermatitis; however, these assumptions remain unproven. There is no documentation of interhuman transmission.

Epidemiology

The literature reports 300 cases of asymmetric periflexural exanthem of childhood from Europe, the United States, and Canada. APEC is quite frequent in France and Italy compared to other geographical areas.[8] It occurs year-round, with a peak during winter and spring, again pointing to this disorder's potential viral origin.

Race  

This condition predominantly affects individuals from light-skinned ethnic groups, a fact that is unexplained. More extensive study is necessary to confirm this hypothesis.

Sex

This dermatosis affects females twice as frequently as males, with an estimated female-to-male ratio of 2 to 1.[9]

Age

APEC affects children aged mostly between the ages of 2 and 3 years. It can also affect adults, although less frequently.[10][11][12]

Pathophysiology

Several authors have suggested the viral origin of asymmetric periflexural exanthem of childhood. Considering the unilateral distribution of the lesions, Neidermeir et al had proposed the hypothesis of increased responsiveness of the affected side of the body to the viral particles.[13]

Histopathology

Microscopic examination of asymmetric periflexural exanthem of childhood is unspecific.[2]  While uncommon, some practitioners have performed a cutaneous biopsy, and when examined microscopically, it may reveal a perivascular, interstitial, and periadnexal lymphohistiocytic infiltrate in the dermis. A histological examination may also reveal epidermal spongiosis and lymphocytic infiltration of the epidermal portion of the eccrine ducts.

History and Physical

The initial presentation is classically unilateral and presents as a macular-papular scarlatiniform eruption that starts in 1 axillary fold. Still, it can also begin in other flexures, such as the thigh, flank, or inguinal fold. Subsequently, after 10 to 15 days, the rash may spread to involve the thorax, the corresponding arm, and the contralateral side in 70% of cases, but it generally maintains its asymmetrical nature.[9] Occasionally, the lesions are serpiginous with central blue-gray coloration. In the resolving phase, lesions may become dusky appearing and eventually desquamate. Usually, the eruption spares the face, palms, soles, and mucous membranes. Lichenification is not a typical feature. Itching and mild local lymphadenopathy is present in 50% of cases. Sometimes, other features of viral infection can occur at the onset of the rash, such as a fever, sore throat, vomiting, and diarrhea. General health is not affected, and all symptoms disappear on average between 4 and 6 weeks without recurrences or scars.

Evaluation

Clinical presentation is the basis for diagnosing asymmetric periflexural exanthem of childhood. Laboratory investigations, including viral examinations, are unnecessary to confirm the diagnosis. An elevated erythrocyte sedimentation rate can accompany APEC. The authors recommend no biological or radiological monitoring.

Treatment / Management

Managing asymmetric periflexural exanthem of childhood does not require specific medical treatment. Mild to mid-potency topical steroids may be used cautiously to control inflammation, though this approach results in a minimal response. Oral antihistamines and moisturizers are an option in cases of pruritus.

Differential Diagnosis

Although several conditions may mimic asymmetric periflexural exanthem of childhood, they do not share the same unilateral distribution. A common misdiagnosis for the eruption is contact dermatitis, which can be unilateral but more pruritic. The morbilliform form of APEC may mimic the non-specific viral exanthems, drug-related eruptions, miliaria, atypical pityriasis rosea, Gianotti-Crosti syndrome, superficial fungal infections, scabies, and scarlet fever. Pityriasis rosea is common among schooled children and young adults. APEC is similar to pityriasis rosea in seasonality, duration, and self-limited character. The infectious origin may explain the clinical resemblance between these different conditions.

Miliaria is usually symmetric and develops on the neck and the upper part of the body. Gianotti-Crosti syndrome and APEC develop in the same age group and manifest by papular exanthem. However, in the case of Gianotti-Crosti syndrome, the eruption is always symmetric and accompanied by lymphadenopathy and, in many patients, hepatosplenomegaly.

Prognosis

The prognosis is excellent; the course of asymmetric periflexural exanthem of childhood is self-limited and spontaneously resolves in 4 to 6 weeks without specific medical intervention.[1][14] Although the pathology is benign, the skin lesions may be a cause of significant concern to the patient and caregivers. 

Complications

No systemic complications or recurrences have been noted previously by authors.

Deterrence and Patient Education

Parents should be educated and reassured that asymmetric periflexural exanthem of childhood is benign and self-limited and disappears in a few weeks. Specific investigations and treatments are not required since the dermatosis is usually asymptomatic and does not adversely affect general health.

Enhancing Healthcare Team Outcomes

Asymmetric periflexural exanthem of childhood is a rare condition usually misdiagnosed by primary care providers and dermatologists. Pediatricians must be aware of and contribute to diagnosing this dermatosis to prevent unnecessary examinations and reassure parents about the benign course of the condition. An interprofessional team approach can best address this relatively benign condition, provide reassurance, and prevent misdiagnosis and resultant improper medication prescribing.