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A 10-month-old male with a rash in the axillae
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An otherwise healthy 10-month-old male presented to clinic with a several-week history of rash. His parents reported that the rash started on the right arm and axillae, and spread down the torso to the right leg (Figures 1 and 2). The family reported a fever a few weeks before the rash started but no associated respiratory or gastrointestinal symptoms. The rash was asymptomatic and had not been treated. On examination, he had numerous 2- to 3-mm erythematous, scaling papules on the right axillae extending to the arms, legs, and trunk.
He took no oral medications and had no known allergies. Of note, the patient’s brother had developed a similar rash a few weeks before that had resolved on its own.
Source: Aditi Murthy, MD
Can you spot the rash?
A. Unilateral laterothoracic
exanthem
B. Varicella zoster
C. Scabies
D. Contact dermatitis
E. Atopic dermatitis
Case discussion
Unilateral laterothoracic exanthem (ULTE), also known as asymmetric periflexural exanthem of childhood, is a unique eruption that occurs in young children. It tends to present as mildly pruritic, erythematous papules and plaques that begin in the axilla and spread outward. Despite the name, the rash can eventually spread to become more generalized. It is thought to be triggered by a virus, although no specific virus has been implicated. ULTE tends to be seasonal in nature, suggesting a seasonal infectious etiology. Treatment consists of supportive care, mild potency topical steroids and antihistamines, if needed, for pruritus. The rash tends to resolve without treatment within a few weeks in most patients.
The differential diagnoses of unilateral rashes in children include herpes zoster, contact dermatitis, scabies and lichen striatus. Herpes zoster can occur in both immunocompetent and immunocompromised children either as sequelae of vaccination or from wild-type varicella. Zoster in children presents as an acute vesicular eruption in a dermatomal distribution. Pain or pruritus can be presenting features. Treatment consists of systemic antivirals and supportive therapy.
Scabies is important in the differential diagnosis of a polymorphous eruption in a child especially for a rash involving flexural areas. Scabies is caused by the mite Sarcoptes scabiei, which most commonly is transferred from one person to another. It can be intensely pruritic and presents with papules, papulonodules, eczematous patches and excoriations. Important sites to assess are axillae, groin, umbilicus, wrists, palms and interdigital spaces of fingers and toes. The first-line treatment is a topical scabicide, such as 5% permethrin cream.
Both contact dermatitis and atopic dermatitis are important to consider in the differential diagnosis. Unlike this patient’s rash, atopic dermatitis (eczema) is usually more symmetric. Classic eczema typically consists of ill-defined, scaly, erythematous patches accompanied by significant pruritus. In infants, it would be more common to involve the face and extensor extremities rather than the folds. In older children, flexural areas would also be prone to involvement. Topical corticosteroids and emollients are mainstays of therapy.
Contact dermatitis can occur on any site that has been exposed to a culprit allergen. Unlike the scattered papules seen in our patient, contact dermatitis usually presents with well-demarcated geometric shapes that serve as a clue to an outside etiology. Unlike in our patient, contact dermatitis is usually pruritic and should respond well to topical corticosteroids or occasionally warrants oral corticosteroids if severe.
ULTE is a unique eruption seen in children following a viral illness and can easily be recognized by the classic presentation of scaly, erythematous papules that begin in the axilla and spread downward on one side of the body.
- References:
- McCuaig CC, et al .J Am Acad Dermatol. 1996 Jun;34(6):979-984.
- Paller AS, et al. Hurwitz Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. 5th ed. Elsevier; London; 2016.
- For more information:
- Aditi Murthy, MD, is a pediatric dermatology fellow at The Children’s Hospital of Philadelphia. She can be reached at MurthyA1@email.chop.edu.
- Marissa J. Perman, MD, is an attending physician at The Children’s Hospital of Philadelphia.
Disclosures: Murthy and Perman report no relevant financial disclosures.