Asymmetric periflexural exanthem of childhood (APEC) is a dermatosis that was first described in 1962 by Brunner et al. as ‘’a new papular erythema’’.
In 1986, Taieb et al. also described this disease, then suggested the term APEC in a second publication in 1993. APEC is a distinctive and a self-limited exanthem which classically affects children and less frequently adults . The precise etiology of this condition is unknown, but the hypothesis of a viral cause seems to be plausible but remains unconfirmed. APEC manifests as a unilateral papular exanthem with stereotypical morphology and distribution. Usually, laboratory investigations and biopsy are not necessary for this condition because of its excellent prognosis and its self-limited character in a few weeks.
The etiology of this dermatosis remains unknown despite an active search for a causative agent. However, there are many factors in favor of 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.
Virologic examination seems to support this assumption. However, more than one virus appears to be capable of evoking the disease.
Duarte et al. considered a relationship to infections with parainfluenza virus 2 or 3, adenovirus, human herpesvirus 6 or 7, and Epstein–Barr virus.
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. Parvovirus B19 has been reported as a viral infection associated with APEC in two female children and one adult patient.
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 about 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. It occurs year-round with a peak during winter and spring which again points to the potential viral origin of this disorder.
This condition predominantly affects individuals from light-skinned ethnic groups. This fact is unexplained. More extensive study is necessary to confirm this hypothesis.
This dermatosis tends to affect females twice as frequently than males, with an estimated female-to-male ratio of 2 to 1.
As mentioned previously, several authors have suggested the viral origin of asymmetric periflexural exanthem of childhood. In consideration of 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.
Microscopic examination of asymmetric periflexural exanthem of childhood is unspecific. 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.
The initial presentation is classically unilateral and presents as a macular-papular scarlatiniform eruption that starts in one axillary fold, but 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. 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 will be present in about 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.
The basis for the diagnosis of asymmetric periflexural exanthem of childhood is on clinical presentation. Laboratory investigations including viral examinations are not necessary to confirm the diagnosis. An elevated erythrocyte sedimentation rate can accompany APEC. Authors recommend no biological or radiological monitoring.
The management of 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 non-specific viral exanthems, the 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 terms of 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 are both manifested 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. Although the pathology is benign, the skin lesions may be a cause of significant concern to the patient and caregivers.
No systemic complications or recurrences have been noted previously by authors.
Parents should be educated and reassured that asymmetric periflexural exanthem of childhood is a benign and a self-limited exanthem that 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.
Asymmetric periflexural exanthem of childhood is a rare condition which is usually misdiagnosed by nurse practitioners, primary care providers, and dermatologists. Pediatricians must be aware and contribute to the diagnosis of this dermatosis to prevent unnecessary examinations and to reassure parents about the benign course of the condition. A multidisciplinary team approach involving physicians (both MDs and DOs), mid-level practitioners (NPs and PAs), and nursing can best address this relatively benign condition, and provide reassurance and prevent misdiagnosis and resultant improper prescribing of medication.
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