A 4-mm punch biopsy confirmed that this was a case of blaschkitis. This uncommon condition is referred to as adult blaschkitis because it resembles lichen striatus, a linear erythematous papular eruption usually seen in children younger than 15 years of age that erupts along Blaschko lines. The biopsy in this case helped to rule out lichen planus, which can also manifest with an erythematous papular eruption along Blaschko lines.
Adult blaschkitis is thought to be a hypersensitivity reaction involving T cells. It has been linked to medication use, insect stings, trauma, and autoimmune disease.1 The characteristic linear pattern is due to the inflammatory response following the Blaschko lines of keratinocytes that migrated during the embryonic phase.1 Post-inflammatory hyperpigmentation is a frequent complication. Topical steroids often help with the itching, but do not usually make the lesions go away. There have been better results in reducing itching and lesion prominence with intralesional steroid injections, topical calcipotriol, or calcineurin inhibitors.1 The inflammation usually spontaneously resolves over 3 to 12 months.
The patient was advised that the condition is benign and would likely resolve on its own over time. She was counseled that since the clobetasol was helping with her itching, she could use it (sparingly) as needed. She was cautioned that prolonged usage could lead to skin atrophy.
Photo courtesy of Daniel Stulberg, MD. Text courtesy of Daniel Stulberg, MD, FAAFP, Department of Family and Community Medicine, University of New Mexico School of Medicine, Albuquerque.