This 12 year old girl has odd bumps on her arm.
What is your diagnosis?
A 12 year old girl developed a few violet colored bumps on her upper, outer arm. Over several months, she developed more, in a linear pattern, moving down her arm. After about 1 year, the original bumps were starting to disappear, and it appeared that they were resolving in the order that they had appeared. They were mildly pruritic. The girl was otherwise healthy. No other family history of similar rashes.
This is a very curious eruption that occurs in children approximate ages 2 to 14. A small group of papules initially form and they progress and elongate, usually down an arm or down or leg, forming a linear group of papules. Lichen striatus can also occur in a circular pattern, especially around the mouth and on the backs of the hands. The lesions will usually develop and appear over nine to 12 months. At that point, they will disappear in the same order that they appeared. Sometimes the lesions can be very subtle, and sometimes they can be real thick and scaly like true lichen planus. Histologically, the resemble lichen planus but are considered a distinct entity.
The pearl on this one is to reassure parents that it is a curious disorder of no long-term consequence and that the lesions will disappear in the order they appeared. If the lesions are symptomatic, especially pruritic, topical anti-inflammatories can be employed. Sometimes the lesions can also be associated with dyschromia, either hypo- or hyperpigmentation. This too will fade with time.
Charles E. Crutchfield III, MD
Clinical Adjunct Associate Professor of Dermatology
University of Minnesota Medical School
Medical Director, Crutchfield Dermatology