Incidence estimates for lichen planopilaris and frontal fibrosing alopecia in a New York City health care system.

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are scarring alopecias that cause significant distress and psychological morbidity. Limited studies have been performed examining the epidemiology of FFA and LPP. We performed a retrospective case cohort analysis by querying for patients with the ICD 10 code L66.