Antoni Leśniowski (January 28, 1867 – April 4, 1940) was a Polish surgeon, credited with publishing what may have been the earliest reports of the condition which later became known as Crohn's disease.
From 1892 to 1912 he worked as a surgeon at the Infant Jesus Hospital in Warsaw, specialising in urology.
On May 10, 1903, Medycyna, a weekly medical newspaper, published an article in which he described several cases of intestinal disease, concluding in at least one case: "we suspected a chronic inflammatory process in the wall of the gut.
"[1] He wrote three further articles describing cases for the Pamiętnik Towarzystwa Lekarskiego Warszawskiego (Annals of the Warsaw Medical Association) between 1903 and 1905, consistent with what is now known as Crohn's disease, although the evidence is not conclusive.
[2] In one of these articles, in 1904, he reported a meeting of the Warsaw Medical Society, at which he presented a surgical specimen of an inflammatory tumour of the terminal ileum with a fistula to the ascending colon.