Epidemiological evidence of the association between lichen planus and two immune-related diseases. Alopecia areata and ulcerative colitis. Gruppo Italiano Studi Epidemiologici in Dermatologia.

Between September 1986 and February 1988, a case-control study involving 27 Italian dermatological centers collaborating in the Gruppo Italiano Studi Epidemiologici in Dermatologia was conducted, concerning the relationship between history of several medical conditions and exposures to drugs and the risk of lichen planus. The cases were all consecutive patients with a new diagnosis of lichen planus, and the controls were patients under dermatological care observed under the same conditions. A total of 711 cases and 1395 controls met the admission criteria and were interviewed by trained investigators. Patients with histories of alopecia areata were found to be at risk for lichen planus (relative risk = 2.7; 95% confidence interval, 1.1 to 6.5). Five patients (0.7%) in the group with lichen planus had a history of ulcerative colitis, while none of the controls had this disease. The risk of lichen planus was also increased in patients with a history of chronic active hepatitis, but this increase was not statistically significant (relative risk = 4.7; 95% confidence interval, 0.7 to 29.4).