Familial lichen planus. More frequent than previously suggested?

In a follow-up study of 140 patients with lichen planus we found fifteen patients with a clinically and/or histologically verified family history of the disease, which gives a percentage much higher than that found in previous studies. The reason for this discrepancy might be caused by difficulties in the detection of the disease in family members. Familial lichen planus was found to be different from nonfamilial lichen planus, especially in its effect on young persons and in being a more widespread type with a tendency to result in relapse. The high incidence of familial lichen planus supports the hypothesis that genetic factors are of etiologic importance in lichen planus.