A distinctive pityriasiform and lichenoid eruption of the extremities, particularly of the elbows and knees, occurs in children 4 to 12 years old. The lesions recur in the summer months and may be attributed to friction during play on abrasive surfaces. Sources of irritation are sandpiles, sandy beaches, rugs with short pile, upholstered furniture, and wool blankets on which the children kneel and crawl. Patients are presumed to possess a peculiar cutaneous predisposition which elicits this characteristic papular lichenification. Healing without residual changes follows avoidance of frictional trauma and treatment with mild topical medication.
WAISMAN M, GABLES C, SUTTON RL. Frictional Lichenoid Eruption in Children: Recurrent Pityriasis of the Elbows and Knees. Arch Dermatol. 1966;94(5):592–593. doi:10.1001/archderm.1966.01600290066011
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