Linear terra firma-forme dermatosis of the midline back.

Terra firma-forme dermatosis (TFFD) is a benign and likely underdiagnosed disorder with relatively few reports in the literature. A 46-year-old woman presented to our clinic with a 3-year history of linear TFFD extending from the upper sacrum to the midline upper back. It initially was thought to be acanthosis nigricans or lichen simplex chronicus, and a topical steroid cream was applied without success. The lesion ultimately was removed by rubbing with isopropyl alcohol, which confirmed a diagnosis of TFFD. Due to its ability to mimic other skin diseases, TFFD should be considered when patients present with hyperkeratotic hyperpigmented lesions.