Kyrle's disease.

A fifty-nine year old man is reported herein with a hyperkeratotic papular eruption that clinically and histologically was compatible with Kyrle's disease (hyperkeratosis follicularis et parafollicularis in cutem penetrans). Treatment with tretinoin (topical vitamine A acid) resulted in a severe inflammatory reactions in the lesions which persisted for four monthes and did not prevent a mild recurrence of the disease. The clinical and histologic differential diagnosis is reviewed perforating folliculitis, reactive perforating collagenosis, and elastosis perforans serpiginosa. The close similarity between Kyrle's disease and perforating folliculitis often makes absolute diagnosis very difficult.