What are the differences between Kyrle’s disease, reactive perforating collagenosis, and perforating folliculitis?

All three disorders are classified as perforating diseases; however, as originally defined, Kyrle’s disease is due to an abnormal clone of keratinocytes that perforates through the epidermis down into the dermis. In contrast, reactive perforating collagenosis is a disease in which presumably abnormal collagen is being extruded from the dermis through the epidermis. Perforating folliculitis is a disease characterized by follicular plugs and curled-up hairs that perforate through the follicle into the dermis. Kyrle’s disease is a controversial entity, with some authorities doubting its existence.