Idiopathic lichen planus: treatment with metronidazole

A retrospective cohort study of the efficacy of metronidazole in oral lichen planus

Lichen planus (LP) is an inflammatory dermatosis with mucosal variants, including oral LP (OLP). OLP has a relapsing chronic course and may significantly affect a patient's quality of life. We analysed the efficacy of metronidazole as a treatment for OLP via a retrospective chart review of patients with a diagnosis of OLP seen at our institution over 10 years. Thirty patients with OLP were treated with metronidazole 500 mg twice daily. Most patients (n = 18; 60%) showed improvement with metronidazole, including 10 (33%) who experienced complete resolution of symptoms. Our results were limited by the retrospective nature of the review and the relatively small cohort size. Given the efficacy, mild side-effect profile and the less immunosuppressive nature of metronidazole vs. alternative systemic treatment options, metronidazole is a reasonable option to try in patients with symptomatic OLP who have failed topical treatment options.

Crucial Role of Microbiota in Experimental Psoriasis Revealed by a Gnotobiotic Mouse Model

Psoriatic patients have altered microbiota, both in the intestine and on the skin. It is not clear, however, whether this is a cause or consequence of the disease. In this study, using an experimental mouse model of psoriasis induced by imiquimod (IMQ), we show that oral treatment with a broad spectrum of antibiotics (MIX) or metronidazole (MET) alone mitigates the severity of skin inflammation through downregulation of Th17 immune response in conventional mice. Since some antibiotics, including MET, can influence immune system reactivity, we also evaluated the effect of MIX in the same model under germ-free (GF) conditions. GF mice treated with MET did not show milder signs of imiquimod-induced skin inflammation (IISI) which supports the conclusion that the therapeutic effect is mediated by changes in microbiota composition. Moreover, compared to controls, mice treated with MIX had a significantly higher abundance of the genus Lactobacillus in the intestine and on the skin. Mice treated with MET had a significantly higher abundance of the genera Bifidobacterium and Enterococcus both on the skin and in the intestine and of Parabacteroides distasonis in the intestine. Additionally, GF mice and mice monocolonized with either Lactobacillus plantarum or segmented filamentous bacteria (SFB) were more resistant to IISI than conventional mice. Interestingly, compared to GF mice, IMQ induced a higher degree of systemic Th17 activation in mice monocolonized with SFB but not with L. plantarum. The present findings provide evidence that intestinal and skin microbiota directly regulates IISI and emphasizes the importance of microbiota in the pathogenesis of psoriasis.

Oral metronidazole treatment of lichen planus

BACKGROUND

Oral metronidazole has been reported to be effective in some patients with idiopathic lichen planus (LP) who did not have concomitant protozoal infections of the intestinal or genital tracts.

OBJECTIVE

Our purpose was to evaluate the efficacy of this drug in the treatment of generalized LP.

METHODS

Nineteen patients with LP who were free from intestinal and genital protozoal infections were treated with oral metronidazole, 500 mg twice daily, for 20 to 60 days and were followed up for a period of 5 to 36 months.

RESULTS

Fifteen patients (78.9%) improved with metronidazole treatment. Complete response was observed in 13 patients (7 women and 6 men). Two patients responded partially. Worsening of the lesions was observed in 1 of the 4 nonresponding patients.

CONCLUSION

Metronidazole may be an alternative therapy for the treatment of generalized LP. Its immunomodulatory activity seems to be a possible mechanism of action besides its antimicrobial activity.

New and emerging therapies for lichenoid dermatoses

Lichenoid dermatoses comprise a significant proportion of dermatologic conditions. The pathophysiologic mechanisms are unclear for many such dermatoses making treatment difficult. Ongoing research into these mechanisms is allowing more directed intervention possible. This article describes some of the recent experiences in the therapy of lichen planus, lichen nitidus, toxic epidermal necrolysis, and graft versus host disease.

Lichen planus

Lichen Planus is a relatively common inflammatory dermatosis of unknown origin. The present review summarizes the histological and clinical features of lichen planus and variants, including lichenoid drug reactions, are described. Possible mechanisms of pathogenesis of lichen planus are reviewed. The development of malignancy in association with lichen planus and the association with hepatitis are discussed. Treatment options for the more difficult manifestations of lichen planus are proposed.