In 1932, Dr. Crohn and his two colleagues, Dr. Leon Ginzburg and Dr. Gordon D. Oppenheimer, published an important paper describing the features of the then relatively unknown condition. They described fourteen cases, characterizing Crohn's disease as "Terminal Ileitis: A new clinical entity"; the description was changed to "Regional ileitis" on publication. It is by virtue of alphabetization rather than contribution that Crohn's name appeared as first author: because this was the first time the condition was reported in a widely-read journal, and the disease has come to be known as Crohn's Disease for reasons of publicity rather than precedence.
At the time he described the disease, Crohn was a practitioner and usually admitted his patients to the Mount Sinai Hospital in New York for their operations. Crohn gradually became more attached to the Mount Sinai Hospital, where he worked with the neurologist Bernard Sachs (1858-1944). There he soon built a very large and successful reception for patients with granulomatous enterocolitis and eventually was made chief of the department of gastroenterology. As such he was highly respected through all of his professional career and received numerous patients from all over the USA, some even from Europe.
Some of his initial research into the causes of the disease was centered around his personal conviction that it was caused by the same pathogen, a bacterium called Mycobacterium paratuberculosis, responsible for the similar condition that afflicts cattle called Johne's disease. However he was unable to isolate the pathogen (most likely due to the fact that M. paratuberculosis sheds its cellular wall in humans and takes the form of a spheroplast, making it virtually undetectable under optical microscope). This theory has resurfaced in recent years and has been lent more credence with the arrival of more sophisticated methods of identifying MAP bacteria.
After retirement, Crohn moved to a mansion-like building situated in the interior of Connecticut. He spent his later years rather like a recluse, as all communications were handled by the Department of Public Relations at the Mount Sinai Hospital. As the hospital's greatest PR-asset, Crohn was treated with great respect.