Asymmetric Periflexural Exanthem of Childhood - Causes, Diagnosis, and Treatment

Introduction

Asymmetric periflexural exanthem of childhood (APEC) is an uncommon clinical condition characterized by the presence of rashes on the sides of the trunk in young children. It is also called the later thoracic exanthem. In 2014, a new name was proposed for this condition called superimposed lateralized exanthem of childhood.

What Is the History of Asymmetric Periflexural Exanthem of Childhood?

Brunner et al. mentioned a "new papular erythema" in 1962 among 75 children aged 6 months to five years. Then, in 1992, Bodemer and de Prost reported many cases (nearly 18 children), and the condition was named unilateral later thoracic exanthem (ULE). The term asymmetric periflexural exanthem of childhood (APEC) was suggested by Taieb and colleagues in 1993 to replace ULE, as the previous name did not mention the complete presentation of this skin lesion. APEC has been reported in the literature as a rare exanthema that is self-limiting and resolves spontaneously. The etiology is not clear, and more commonly, children have been

affected. Only three adults have been known to be affected by this condition, as per the literature.

How Is It Caused?

The exact etiology of this skin condition is not known. The specific virus or other microorganism causing it has not been identified.

What Is the Pathophysiology of Asymmetric Periflexural Exanthem of Childhood?

Several authors have proposed a viral origin for asymmetric periflexural exanthem in childhood. Given the unilateral distribution of the lesions, Neidermeir et al. suggested that the affected side of the body may be more responsive to viral particles.

What Is the Mechanism Behind this Condition?

The cause of childhood asymmetric periflexural exanthems has not been established. Thus, the pathophysiology of this condition is unclear. The possible etiology is thought to be a virus due to the history of the patient, like the presentation age, more than one child affected in a family, no response to antibiotic treatments, serologic findings, and more incidence of these cases during spring and winter. However, this possibility has not yet been proven, as there is no evidence for it. The most common manifestation of this condition is exanthem, which is rashes on the body with a typical distribution and presentation in the body. Since it is self-limiting, a biopsy is rarely done.

What Is the Distribution of This Condition?

• Frequency: The literature shows that nearly 300 children are affected by this condition. Most cases have been reported in the United States, Europe, and Canada.

• Gender: This condition affects females more commonly than males and the ratio between females to males is 2:1. Thus, females are more prone to develop this condition when compared to males.

• Race: Light-skinned people tend to develop it more commonly than dark-skinned people.

• Age: The literature reports that the average age at which this condition can manifest is six years, but children between four months and ten years can be affected. Three to four cases have also been mentioned in adults.

How Is the Prognosis?

The prognosis for asymmetric periflexural exanthem of childhood is excellent, as it is self-limiting and typically resolves on its own within four to six weeks without medical intervention. Despite being benign, the skin lesions can cause significant concern for both the patient and their caregivers.

How Can It Be Diagnosed?

• History: When the person visits the physician, the person will be asked about the signs and symptoms the child is facing, which can be a current and/or recent episode of infection related to the upper respiratory tract, swelling of lymph nodes, fever, otitis media, or loose motions. Most of the children tend to be asymptomatic and appear to be healthy without any other medical condition. In rare cases, more than one child in the family might have asymmetric periflexural exanthem of childhood. Nearly 50 percent of the affected children tend to have mild pruritus.

• Physical Examination: On physical examination, the child will have the primary (pathognomonic) lesion, which is a small red papule with a surrounding pale border. The more common appearance includes papules or rashes, which can occasionally be associated with fine scaling.

In the beginning stages, the lesions affect one side and usually start to appear near the axillae, lateral body, and upper inner arm or groin. Later on, the lesion may progress to develop on both sides of the body and tend to be asymmetric.

There are four sequential stages of the lesions, which include the following:

1. The eczematous stage is when the initial lesions occur on the axillary and lateral chest walls.

2. Coalescence stages in which the lesions extend to the center of the body, hands, and legs. They tend to be separated by areas of normal skin.

3. Regression stage in which the older lesions tend to develop into a dusky-gray center.

4. The desquamation stage is in which the remaining residual scale develops and resolves later.

The face, palms, soles, and mucous membranes are not affected by this condition.

• Laboratory Tests: There are no specific laboratory tests that are required to diagnose APEC. However, the erythrocyte sedimentation rate can be elevated in these children. Parvovirus B19 has been seen to be associated with asymmetric periflexural exanthemism of childhood in many children. In rare cases, serologic results can become positive for respiratory pathogens like adenovirus and parainfluenza virus. Also, many studies have revealed negative serologic results for hepatitis, Mycoplasma organisms, borreliosis, Epstein-Barr virus, cytomegalovirus, coxsackievirus, HIV, toxoplasmosis, and rickettsiae.

What Are the Other Conditions that Mimic this Condition?

The various conditions that can be similar to APEC are as follows:

• Allergic contact dermatitis (skin inflammation due to allergic reaction).

• Miliaria (skin rash due to blocked sweat ducts).

• Tinea Corporis (a fungal infection causing a ring-shaped rash on the body).

• Milia (small, white bumps on the skin due to keratin).

• Lichen striatus (benign skin condition causing linear rash).

• Pityriasis Rosea (common skin rash with distinctive "Christmas tree" pattern).

• Dermatologic Manifestations of Gianotti-Crosti Syndrome.

• Scabies (contagious skin infestation caused by mites, intense itching).

• Scarlet Fever (bacterial infection causing rash, fever, sore throat).

How Can It Be Treated?

As mentioned earlier, it is a self-limiting condition and, thus, does not require any specific medical management. Although, low-potency topical steroids can be used for symptomatic relief. Hydroxyzine can be helpful to manage pruritus. Moisturizers are also recommended to manage pruritus and fine scaling.

Conclusion

Asymmetric periflexural exanthem of childhood (APEC), also called later thoracic exanthem, is a clinical condition affecting the skin of children. The etiology is not known. Although it is self-limiting, symptomatic relief can be provided using some topical medicines. Online medical platforms have emerged recently, which have made communicating with physicians easy and comfortable. By consulting a specialist, a person can learn about the causes, management, and other details of this condition.