Type: Term Pronunciation: yah′dah-sōn Definitions: 1. Josef, German dermatologist in Switzerland, 1863-1936; introduced the patch test for contact dermatitis. See: Jadassohn nevus, Borst-Jadassohn type intraepidermal epithelioma, Jadassohn-Pellizzari anetoderma, Franceschetti-Jadassohn syndrome, Jadassohn-Lewandowski syndrome ...