ULE?

Abstract: 4 yo girl with 3 week hx of papular eruption left axilla
HPI: This otherwise healthy four year old girl has had a mildly pruritic papular eruption which began in the left axilla with a dermatitic appearance and spread centrifugally where it appeared more papular. There was no antecedent illness. The eruption was first seen on 12/23/2010, cleared after a few days and they reoccurred. The child is not bothered by it. No animals at home and no other family members similarly affected.
O/E: Discrete erythematous papules in the left axilla and surrounding areas. The individual lesions are 3 - 5 mm in diameter. The right axilla and thoracic area are clear. There is left axcillary adenopathy
Clinical Photos: 12/31/2010
Left Axilla

Right Axilla
Lab: none

Diagnosis: Unilateral Laterothoracic Exanthem.

DDx: The lesions look like bites. Against that is the lack of symptoms, the unilateral location, and no likely cause of bites. Contact dermatitis seems unlikely.

Discussion: This is an unusual entity but the child seems well otherwise and I have recommended no treatment for present. I have not seen ULE before (to my knowledge); yet this seems the likely diagnosis. Unfortunately, the pictures in the textbooks are not very good. I suspect, that like Gianotti-Crosti, ULE may be caused by a number of viruses and that it will be difficult to come up with an etiology. The clinical appearance seems to be protean, but the distribution aids in making a diagnosis.

Reference:
1. Emedicine.com has a good chapter, however, they use the name "Asymmetric Periflexural Exanthem of Childhood."

2. McCuaig CC, et. al. Unilateral laterothoracic exanthem. A clinicopathologic study of forty-eight patients. J Am Acad Dermatol. 1996 Jun;34(6):979-84.
Department of Pediatrics, Hôpital Sainte-Justine, Montreal, Quebec, Canada.
Abstract
BACKGROUND: Four years ago, we began seeing young children with an unusual, predominantly unilateral, morbilliform and eczematous, self-limited cutaneous eruption. It appeared to correspond to unilateral laterothoracic exanthem (ULE) reported from France and to an eruption described as "a new papular erythema of childhood" in the United States.
OBJECTIVE: We conducted a prospective study of ULE to define its clinical evolution, pathology, and therapy. In addition, we performed epidemiologic and microbiologic investigations in an attempt to determine the cause of ULE.
METHOD: We studied 48 children with ULE. In some patients, blood, urine, stool, as well as skin biopsy specimens were analyzed.
RESULTS: ULE is a morbilliform, eczematous eruption that often begins close to the axilla and spreads to become bilateral, although it usually retains a unilateral predominance. Patients' mean age at onset is 24.3 months, with a female predominance (2:1) and mean duration of 5 weeks, followed by spontaneous resolution that may or may not be improved with topical corticosteroids. It is characterized by a unique eccrine lymphocytic infiltration. Although signs of infection were reported by most patients, no one infectious agent was identified. No significant epidemiologic factor was found.
CONCLUSION: ULE, in young children, is a self-limited morbilliform and scarlatiniform eruption that may represent a specific skin reaction to one or more infectious agents.

Follow-up Note: The patient's symptoms continued to wax and wane and she was seen by a pediatric dermatologist. At that time, there was just one lesion in the left axilla ( see picture) and a diagnosis of psoriasis was made. There were no other stigmata for psoriasis. If this is the case, the initial picture did not suggest that. Since the sole lesion present now is a plaque in the left axilla, if this turns out difficult to control with topical steroids, consideration to using tacrolimus should be given.





References:
Tacrolimus ointment is effective for psoriasis on the face and intertriginous areas in pediatric patients.
Brune A, Miller DW, Lin P, Cotrim-Russi D, Paller AS. Pediatr Dermatol. 2007 Jan-Feb;24(1):76-80.
Abstract
Children with psoriasis often have involvement of the face and intertriginous areas. While corticosteroids have been the mainstay of treatment for plaque-type psoriasis, the face and intertriginous areas are more sensitive to local effects of topical steroid use such as cutaneous atrophy. Topical tacrolimus has shown promise in adult patients as an alternative antiinflammatory without the cutaneous side effects of steroids. Eleven patients between 6 and 15 years of age with facial or inverse psoriasis were evaluated in a 6-month, single-center, open-label trial. Clinical evaluations were made at baseline and days 30, 90, and 180. Severity was assessed using the physician's global assessment of improvement relative to baseline, a 6-point rating scale for signs of disease (erythema, infiltration, desquamation), and an overall severity score. Within the first 30 days of treatment, every patient had cleared or achieved excellent improvement with the use of tacrolimus ointment. Statistically significant improvement was achieved in each sign of disease and the overall severity score. The only adverse event reported in 6 months of observation was significant pruritus in one patient. We therefore conclude that tacrolimus ointment is an effective treatment for psoriasis on the face or intertriginous areas in children.