Familial lichen planus. Another disease or a distinct people?

When lichen planus strikes families, a very rare happening, it is likely to afflict younger members, to erupt more acutely, extensively, and gravely, attacking also nails and mucous membranes, and to recur. Ten patients with familial lichen planus, two each from five distinct Caucasian families, the parents of whom were unrelated by birth, were found to be carrying HLA-B7 statistically more frequently than in the normal population or in those with the characteristic forms of lichen planus. We hint that their genotype might have rendered them susceptible to a pathogen that precipitated their disease.