|What’s this rash on this boys chest?
8 year old boy who developed a mildly pruritic, pink, papular, rash on just the left side of his chest and abdomen. Had a URI about 5 days before the rash appeared. He is otherwise healthy.
What is your diagnosis?
Unilateral laterothoracic exanthem
This is also been called 'asymmetric periflexural exanthem of childhood'. Initially, the rash starts out with pink-red macules and papules located on the lateral side of the trunk and often involving the axilla. As time goes on, the rash can spread generally, but it still has a slightl unilateral predominance. The rash will usually resolve on its own in two to six weeks. Although the precise etiology is idiopathic, it is assumed to be a viral in origin.
It occurs in children ages 6 months to 10 years. The exanthem is usually preceded by an upper respiratory tract infection or gastrointestinal prodrome including fever, diarrhea, and/or rhinitis. This particular patient reported an upper respiratory tract infection that occurred a few days before the rash presented itself. I have seen several cases and sometimes the lesions are very pruritic and other times the patients wouldn't really know that the lesions were present unless they saw them in the mirror. In this particular case, the lesions were very mildly pruritic, and the patient was put on topical class V steroid cream twice daily for 10 days, which resulted in an approximate 95% improvement. The patient had already had the rash for two weeks when I saw him, and a month after the visit, the rash had cleared. It is important to reassure parents that the rash itself will resolve spontaneously in two to six weeks and the only treatment needed is supportive, based on the presence symptoms.
Charles E. Crutchfield III, MD
Clinical Adjunct Associate Professor of Dermatology
University of Minnesota Medical School
Medical Director, Crutchfield Dermatology