A 15-year-old girl presented with a 2-month history of an itchy eruption with a linear arrangement from the dorsolateral side of the left foot to the posterior aspect of the left thigh. She had no relevant medical history or laboratory tests. The lesion was a band-like, interrupted, slightly-erythe- matous plaque, which extended the entire length of the left leg along the lines of Blaschko (Fig. 1A). A skin biopsy was taken from papules with erythema on the left calf area. Histopathologic findings showed a focal, band-like lymphocytic infiltration in the papillary dermis and reticular dermis around the deep follicles and sweat glands (Fig. 2A). Focal parakeratosis, relatively irregular acanthosis, mild intercellular edema with exocytosis, and scattered dyskeratotic cells were observed in the epidermis (Fig. 2B). The linear eruption was diagnosed as lichen striatus based on both clinical and histological features.
Fig. 1. (A) Clinical appearance of the patient with lichen striatus at presentation. (B) Clearance of the lesions after 3 weeks of treatment with topical pimecrolimus.
The pruritus had been moderate and unresponsive to antihistamines. Because of the possibility of steroid atrophy, the patient was instructed to apply 1% pimecrolimus cream (Elidel®, Novartis Pharma, Basel, Switzerland) once daily. The pruritus began to improve after 1 week and completely disappeared within 3 weeks (Fig. 1B). She had no complaints of any burning sensation during the treatment period. There has been no recurrence for 11 months.
Fig. 2. (A) Diffuse inflammatory cell infiltration in the epidermis and focal lymphocytic infiltration in the dermis (H&E, x 40). (B) Focal parakeratosis, relatively irregular acanthosis, mild intercellular edema with exocytosis, and scattered dyskeratotic cells were observed in the epidermis (H&E, x 100).