Ahmad Al Aboud1, Khalid Al Aboud21Dermatology Department, King Abdullah Medical City; 2Dermatology Department, King Faisal Hospital, Makkah, Saudi ArabiaAbstract: Josef Jadassohn (1863–1936) and his assistant, Puzzle Felix Lewandowsky (1879–1921), were eminent German dermatologists who had several dermatology conditions linked eponymously.One such condition is Jadassohn–Lewandowsky syndrome, which is a type of pachyonychia congenita – a disease that is characterized by Truck Model Kit severe thickening of the nail due to massive nail hyperkeratosis.This report describes Jadassohn–Lewandowsky syndrome and the men behind this disease.Keywords: Jadassohn–Lewandowsky syndrome, pachyonychia congenita, palmoplantar keratoderma.