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Asymmetric periflexural exanthem of childhood (APEC) is a rare, self-limited skin condition that primarily affects children, though adults can also be affected. The exact cause of APEC remains unknown, though a viral origin is suspected. Clinically, APEC presents as a unilateral papular rash with a characteristic distribution, typically occurring in the flexural areas of the body. Given its benign nature and spontaneous resolution within a few weeks, extensive laboratory testing or biopsy is generally unnecessary. The prognosis is excellent, with no long-term complications associated with this condition. Through this course, the participant learns how to evaluate, diagnose, and manage APEC, emphasizing its clinical features and natural course. Accurate diagnosis without unnecessary testing is highlighted to avoid overtreatment. Collaborating with an interprofessional team, including dermatologists, pediatricians, and primary care clinicians, enhances patient outcomes by ensuring comprehensive care. This team-based approach ensures appropriate diagnosis, reduces unnecessary interventions, and promotes patient and caregiver education, ultimately improving the management of APEC. Objectives: Differentiate periflexural exanthem of childhood from other similar dermatoses, such as viral exanthems and allergic reactions, through visual assessment. Screen pediatric patients with papular rashes for signs consistent with periflexural exanthem of childhood, particularly in flexural areas. Implement a management plan that emphasizes reassurance and patient education regarding the self-limited nature of periflexural exanthem of childhood. Communicate the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by asymmetric periflexural exanthem. Access free multiple choice questions on this topic.

Asymmetric periflexural exanthem of childhood (APEC) is a dermatosis that was first 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.[3] The precise etiology of this condition is unknown, but the hypothesis of a viral cause seems plausible, which 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.

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.

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] This condition 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 between the ages of 2 and 3; this condition can also affect adults, although less frequently.[10][11][12]

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]

Microscopic examination of asymmetric periflexural exanthem of childhood is unspecific.[2] While uncommon, some clinicians 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.

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 appear dusky 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 are 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.

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.

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.

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 nonspecific 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.

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.

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.

APEC is a rare condition usually misdiagnosed by primary care providers and dermatologists. Pediatric clinicians 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.