Lichen planus of the lips: an intermediate disease between the skin and mucosa? Retrospective clinical study and review of the literature

Background: Lichen planus of the lips (LPL) is not frequently described in the literature. The objective of this study is to investigate the clinical outline, behavior, and prognosis of LPL. Methods: Clinical data of patients with true oral lichen planus (LP) involving the lips, diagnosed and treated at our Oral Medicine Unit (University Federico II of Naples, Italy), have been collected and analyzed. Concurrently, a PubMed search was carried out from 1950 to March 2014 to assess epidemiological and clinical data about LPL. Results: Our case series revealed 13 patients (female/male ratio 0.4) with a mean (± SD) age of 71.85 years (± 6.72). The lower/upper lip involvement ratio was 9, mainly with mixed clinical patterns (76.9%), generally including erosion and mild keratosis. In most cases, the lips were involved with other oral sites but displayed a better evolution of the lesions. The literature review showed 21 reports of LPL (35 patients, female/male ratio 0.4) with a mean (± SD) age of 45.35 years (± 16.19). Conclusions: In the literature, erosive (28.57%) lower lip lesions showed a clear predominance (lower/upper lip ratio 6.5). One case of malignant transformation was also reported. The prevalence of isolated LPL was clearly reported only in two studies, ranging from 0.51% to 8.9%. In our patients, lesions were mostly found at the inner border of the lower vermillion and presented a tendency for self-limitation, or to regression after treatment, like cutaneous lesions. The lip lesions were small and easy to overlook, and therefore the prevalence of these lesions may have been underestimated.