Renbök Phenomenon in a Patient With Alopecia Areata Universalis

The Renbök phenomenon, first reported in 1991, described cases where patients with extensive alopecia areata experienced hair growth within plaques of psoriasis. This phenomenon, also known as the reverse Koebner phenomenon, was observed in 4 initial patients and later in 3 additional cases. It was extended to include patients with mosaic phenomena and those with alopecia areata without associated nevi. Unlike the Koebner phenomenon, which involves psoriasis triggered by trauma or inflammation, the Renbök phenomenon occurs when an inflammatory process is inhibited by psoriasis.