Josef jadassohn--an appreciation on the occasion of his 150th birthday.

Josef Jadassohn was a pioneering dermatologist who influenced the development of his specialty in many ways. He introduced the patch test for detection of hypersensitivity reactions, gave original descriptions of several entities, such as nevus sebaceous, granulosis rubra nasi, and pachyonychia congenita, and edited the Handbuch der Haut- und Geschlechtskrankheiten, the most comprehensive textbook of dermatology ever published. Moreover, Jadassohn left a phalanx of distinguished students, including Felix Lewandowsky, Wilhelm Lutz, Max Jessner, Hans Biberstein, Hermann Pinkus, and Marion B. Sulzberger.