Crohn's Disease: History and Discovery

Crohn's disease bears the name of the New York gastroenterologist Burrill B. Crohn, whose 1932 paper with surgeons Leon Ginzburg and Gordon D. Oppenheimer defined “regional ileitis” as a distinct disease. Yet the condition was described long before 1932 — most clearly by the Scottish surgeon Thomas Kennedy Dalziel in 1913, and arguably as far back as Giovanni Battista Morgagni in 1769. The story of how this illness was recognized, named, and slowly understood is tangled with a genuine priority dispute, with a disease that one of the very authors refused to call by his colleague's name, and with a cause that, nearly a century later, is still not fully known. This page tells that history carefully, distinguishing who described the disease from whose name it carries from who is still searching for its cause.

Earlier Descriptions: Morgagni, Lesniowski, and Dalziel
The 1932 Mount Sinai Paper
Why It Is “Crohn's” — the Naming and Priority Debate
What “Regional Ileitis” Meant
Discovering the Cause: Immune, Genetic, and Microbial Clues
Diagnosis and the Birth of the IBD Concept
Treatment Through the Eras
Modern Understanding
Research Papers and References
Connections

Earlier Descriptions: Morgagni, Lesniowski, and Dalziel

Crohn's disease did not appear in 1932; it was simply named then. A condition matching its description had been recorded, and effectively re-discovered, several times over the preceding centuries. The earliest case usually cited belongs to the great Italian anatomist Giovanni Battista Morgagni (1682–1771), founder of pathological anatomy. In his landmark 1769 work De Sedibus et Causis Morborum (“On the Seats and Causes of Diseases”), Morgagni described the autopsy of a young man — by most accounts about twenty years old — who had died after a long illness of fever, abdominal pain, and bloody diarrhea. The autopsy revealed ulceration, perforation, and inflammation involving the terminal ileum and nearby colon, with enlarged mesenteric lymph nodes: a picture strikingly consistent with Crohn's disease. Because Morgagni's account is a single case read backwards through modern eyes, historians treat it as a probable antecedent rather than a formal description of the disease.

In the early twentieth century the condition surfaced again. The Polish surgeon Antoni Lesniowski reported intestinal cases in 1903 that are now regarded as Crohn's disease, which is why in Poland the illness is traditionally called Lesniowski-Crohn disease. The most important pre-1932 description, however, came from the Scottish abdominal surgeon Thomas Kennedy Dalziel (1861–1924) of the Western Infirmary in Glasgow. In 1913 Dalziel published, in the British Medical Journal, a paper titled “Chronic Interstitial Enteritis,” reporting a series of about nine patients with a chronic inflammatory thickening of the bowel wall.

Dalziel's clinical and pathological account was remarkably complete: he noted the thickened, hose-like segments of intestine, the inflammation extending through the full thickness of the bowel wall, and features that later generations would recognize as granulomas. He even speculated about a possible link to Johne's disease, a chronic bacterial enteritis of cattle — a connection that would echo through the later cause-hunting (see below). For these reasons, medical historians widely credit Dalziel with the first clear description of the entity that would be named after Crohn nineteen years later. His work, published in Britain and overshadowed by the First World War, fell into relative obscurity, which is part of why the eponym ultimately attached to the 1932 American paper rather than to him.

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The 1932 Mount Sinai Paper

The paper that gave the disease its modern identity was presented in May 1932 and published in the Journal of the American Medical Association on October 15, 1932, under the title “Regional Ileitis: A Pathologic and Clinical Entity” (JAMA 1932;99:1323–1329). Its three authors all worked at Mount Sinai Hospital in New York: Burrill Bernard Crohn (1884–1983), a gastroenterologist; Leon Ginzburg (1898–1988), a surgeon; and Gordon D. Oppenheimer (1900–1974), also a surgeon. The patient material came largely from the surgical service of the renowned Mount Sinai surgeon A. A. Berg, whose name does not appear on the paper because he declined authorship.

The achievement of the 1932 paper was not discovery in the sense of seeing something never before seen — Dalziel and others had seen it — but definition. Drawing on a series of fourteen patients, Crohn, Ginzburg, and Oppenheimer assembled the scattered observations into a single, clearly delineated clinical and pathological entity: a chronic inflammation, with characteristic ulceration and scarring, that typically affected the terminal portion of the small intestine (the ileum). They described its symptoms, its surgical and pathological appearance, and its tendency to cause obstruction and fistulas, and they distinguished it from intestinal tuberculosis, with which it had often been confused.

Crucially, the paper was widely read, appeared in the most prominent American medical journal of its day, and arrived in a medical culture ready to receive it. That combination — a clear definition, a major platform, and good timing — is why this paper, rather than Dalziel's earlier and arguably superior one, became the reference point from which the modern understanding of the disease is dated. The original article was considered important enough to be reprinted as a “Landmark Article” in JAMA in 1984 (JAMA 1984;251(1):73–79).

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Why It Is “Crohn's” — the Naming and Priority Debate

The single most interesting historical fact about Crohn's disease is that its name is partly an accident of alphabetical order — and that it was opposed both by an author who felt slighted and by the man it honors. When the 1932 manuscript was submitted to JAMA, the journal's editorial policy at the time was to list authors alphabetically. By that rule, Crohn came before Ginzburg and Oppenheimer, so Crohn's name appeared first. As the entity caught on, clinicians began calling it “Crohn's disease” after the lead author — a convenient shorthand that, by historical convention, attaches an eponym to the first-listed name.

Leon Ginzburg never accepted the label. He believed that he, as the surgeon who had studied the specimens, had made the principal contribution to characterizing the disease, and he felt the alphabetical accident had unfairly erased his role. Late in life he made his case publicly: in a 1986 letter to the journal Gastroenterology he set out the surgical team's original contribution and pushed back against retrospective accounts that, in his view, overstated Crohn's individual role. The historical record now generally treats Ginzburg and Oppenheimer as full and essential collaborators rather than as junior assistants.

More surprising still, Burrill Crohn himself reportedly disliked the eponym. He preferred descriptive names such as “regional ileitis” or “cicatrizing enterocolitis,” which describe what the disease is rather than who wrote about it. By one well-circulated account, when a resolution to officially designate the condition “Crohn's disease” came up at an international gathering, Crohn rose to object and was ruled out of order; the name stuck regardless. The honest summary is therefore this: the disease is named for its first-listed author, the naming was driven by an alphabetical rule rather than by a judgment about who contributed most, and the eponym was contested from the very beginning. Readers should keep the distinction clear — Dalziel best describes the disease's first clear account, the 1932 trio defined and popularized it, and the eponym honors only the alphabetically-first of those three.

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What “Regional Ileitis” Meant

The 1932 title, “regional ileitis,” was chosen with care, and unpacking it explains both what the authors saw and why the term was later abandoned. Ileitis means inflammation of the ileum, the final and longest section of the small intestine. Regional captured the disease's most striking feature: it strikes in segments, leaving sharply demarcated diseased lengths of bowel next to apparently normal stretches — the so-called “skip lesions.” To a surgeon opening the abdomen, an affected segment looked thickened, stiffened, and inflamed, with the inflammation reaching through the entire wall of the intestine rather than being confined to its lining.

That last point — transmural (full-thickness) inflammation — is one of the pathological hallmarks that distinguishes Crohn's disease from ulcerative colitis, where inflammation is largely limited to the innermost lining of the colon. The 1932 authors also documented the complications that follow from deep, full-thickness inflammation: narrowing and obstruction of the bowel from scarring (strictures), and abnormal tunnels burrowing between loops of intestine or out to the skin (fistulas). These features remain central to how the disease is recognized today.

The term “regional ileitis” eventually proved too narrow. As more cases accumulated, physicians realized the same disease could appear anywhere along the digestive tract — from the mouth to the anus — not only in the ileum. Disease confined to the colon, in particular, could not sensibly be called “ileitis” at all. Alternative descriptive terms such as “regional enteritis,” “granulomatous enteritis,” and “granulomatous colitis” were tried, but none fit every presentation. In the end, the very vagueness of an eponym became its advantage: “Crohn's disease” describes the whole entity without committing to any one location, which is one practical reason the name endured despite its contested origins.

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Discovering the Cause: Immune, Genetic, and Microbial Clues

It is important to state plainly, because patients deserve honesty: the cause of Crohn's disease is still not fully known. Nearly a century after 1932, the best understanding is that it arises from a harmful interaction among several factors — an over-reactive immune system, inherited genetic susceptibility, the community of gut microbes (the microbiome), and environmental triggers such as smoking and diet — rather than from any single discoverable agent. What follows is a history of the leading lines of investigation, with hypotheses clearly labeled as such.

The infectious hypothesis is the oldest. Because Crohn's disease so resembles intestinal tuberculosis and Johne's disease (the chronic enteritis of cattle), researchers long suspected a mycobacterium. The leading candidate, pursued for decades, is Mycobacterium avium subspecies paratuberculosis (MAP), the organism that causes Johne's disease — the same link Dalziel had wondered about in 1913. Some studies detect MAP more often in Crohn's patients than in healthy people, but it is also found in healthy individuals, antibiotic treatments aimed at it have given inconsistent results, and no study has shown that eliminating MAP cures the disease. The MAP hypothesis therefore remains unproven and genuinely contested — an intriguing association, not an established cause, and it should be presented as such.

The genetic line of evidence is firmer. It was long observed that Crohn's disease runs in families, hinting at inherited risk. The pivotal breakthrough came in 2001, when two independent teams — one led by Jean-Pierre Hugot and one by Yasunori Ogura (with Gabriel Nunez and colleagues) — reported in Nature that variants in a gene then called NOD2, later renamed CARD15, were associated with susceptibility to Crohn's disease. This was the first identified susceptibility gene for the condition. The NOD2/CARD15 protein helps immune cells sense bacterial components, so its discovery elegantly tied together the immune, genetic, and microbial threads. Later genome-wide studies have since identified well over a hundred additional risk loci, confirming that Crohn's disease is polygenic — shaped by many genes of small effect, no single one of which causes the disease by itself.

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Diagnosis and the Birth of the IBD Concept

One reason Crohn's disease was “discovered” so late — and so often — is that for centuries it was confused with other illnesses, above all intestinal tuberculosis, which can produce a nearly identical thickened, ulcerated, scarred ileum. Part of the lasting value of the 1932 paper was that it drew a firm line between regional ileitis and intestinal TB, allowing the two to be told apart and managed differently. Distinguishing Crohn's disease from its mimics has been a continuous diagnostic project ever since.

Equally important was learning to separate Crohn's disease from its close cousin, ulcerative colitis. Ulcerative colitis had been described in the nineteenth century (Samuel Wilks is generally credited with naming it in 1859), but it took decades after 1932 for clinicians to fully appreciate that these were two distinct chronic inflammatory bowel diseases with overlapping symptoms but different patterns: Crohn's can strike anywhere in the gut, in skip lesions, through the full wall thickness; ulcerative colitis is confined to the colon, is continuous from the rectum upward, and involves mainly the lining. Out of this recognition grew the unifying umbrella term inflammatory bowel disease (IBD), under which both conditions sit. When a colitis cannot be confidently assigned to either, clinicians use the honest label “IBD-unclassified” (or, on a biopsy, “indeterminate colitis”).

The tools for telling these diseases apart improved dramatically over the twentieth century. Early diagnosis relied on the surgeon's eye at the operating table and on barium X-rays, which could reveal the narrowed, “string-like” ileum (the classic “string sign”). The transformative advance was fiber-optic endoscopy and colonoscopy from the late 1960s and 1970s onward, which let physicians see the bowel lining directly and take biopsies — turning diagnosis from inference into direct observation. Later, cross-sectional imaging (CT and MRI enterography), wireless capsule endoscopy, and blood and stool markers such as fecal calprotectin further sharpened both diagnosis and monitoring.

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Treatment Through the Eras

The history of treating Crohn's disease falls into recognizable eras, each defined by what medicine could offer. In the first era, before effective drugs, there was little to do beyond surgery and supportive care. Surgeons removed badly diseased or obstructed segments of bowel, but they soon learned a humbling lesson that shaped all later therapy: Crohn's disease tends to recur at the site of a surgical join, so operating is rarely a cure. This recognition pushed the field toward medical control of inflammation rather than repeated cutting.

The second era began in the 1950s with the discovery that corticosteroids (such as cortisone and later prednisone) could powerfully suppress the inflammation and bring active disease under control — a genuine revolution, though one limited by serious side effects when used long-term. Alongside steroids came the aminosalicylates: sulfasalazine, originally developed for rheumatoid arthritis in the 1940s, was found useful in inflammatory bowel disease, and its active component (5-aminosalicylic acid, or mesalamine) was later isolated. To spare patients from steroid dependence, the immunomodulators followed — azathioprine and its relative 6-mercaptopurine, and later methotrexate — drugs that dampen the overactive immune response more selectively over the long term.

The third era, and the most dramatic since corticosteroids, arrived with the biologics. As researchers traced the molecular machinery of inflammation, a signaling protein called tumor necrosis factor-alpha (TNF-α) emerged as a key driver. Infliximab, an engineered antibody that neutralizes TNF-α, became the first biologic approved for Crohn's disease when the U.S. FDA cleared it in 1998 — a turning point that, for the first time, let many patients heal the bowel lining itself rather than merely blunt symptoms. Other anti-TNF agents (such as adalimumab) and then newer biologic classes targeting different molecules — integrins (vedolizumab) and interleukins (ustekinumab) — followed, along with oral small-molecule drugs such as JAK inhibitors. Today the goal of treatment has shifted from simply relieving symptoms to achieving deep, objectively-confirmed healing of the intestine.

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Modern Understanding

The modern picture of Crohn's disease is best summarized as a chronic, relapsing inflammatory disease of the gut with no single cause, arising when a genetically susceptible immune system reacts abnormally to the intestinal microbiome under the influence of environmental triggers. None of those four elements — genes, immunity, microbes, environment — acts alone; the disease emerges from their interaction. This explains why no “germ” was ever found to satisfy the old infectious hypothesis, and why a single cure has proven elusive: there is no single thing to cure.

That framework also makes sense of long-standing observations that once seemed puzzling. Smoking, for example, is one of the clearest environmental risk factors, worsening Crohn's disease (notably, and confusingly, the opposite of its apparent effect in ulcerative colitis) — concrete evidence that environment matters. The rising incidence of Crohn's disease in industrializing countries points toward changes in diet, hygiene, antibiotic exposure, and the microbiome that come with modern life. Research into the microbiome, into the dozens of risk genes uncovered since NOD2/CARD15, and into the immune pathways targeted by today's biologics all flow directly from the multifactorial model.

Seen as a whole, the history of Crohn's disease is a model of how medical knowledge actually accumulates: a condition glimpsed by Morgagni in 1769, clearly described by Dalziel in 1913, defined and named (somewhat unfairly) after Crohn in 1932, separated from its mimics across the twentieth century, illuminated genetically in 2001, and treated ever more precisely as its biology came into focus. The work is unfinished. The cause is still not fully known, the MAP question is still open, and the search for a cure continues — but each generation has handed the next a sharper picture of a disease that has been quietly afflicting people for far longer than it has had a name. For the clinical details of symptoms, diagnosis, and current management, see the main Crohn's Disease article.

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Research Papers and References

The references below combine the foundational primary papers in the history of Crohn's disease — the 1932 JAMA article and the 2001 NOD2/CARD15 discovery papers — with peer-reviewed historical reviews and curated PubMed topic-search links. Historical primary texts named in the article (Morgagni's De Sedibus et Causis Morborum, 1769; Dalziel's 1913 BMJ paper; Ginzburg's 1986 letter to Gastroenterology) are cited where a stable link exists and otherwise named as historical sources. Each link opens in a new tab.

Crohn BB, Ginzburg L, Oppenheimer GD. Regional ileitis: a pathologic and clinical entity. JAMA. 1932;99(16):1323-1329. — doi:10.1001/jama.1932.02740680019005
Crohn BB, Ginzburg L, Oppenheimer GD. Landmark article Oct 15, 1932. Regional ileitis: a pathological and clinical entity (reprint). JAMA. 1984;251(1):73-79. — PubMed: 6361290
Hugot JP, Chamaillard M, Zouali H, et al. Association of NOD2 leucine-rich repeat variants with susceptibility to Crohn's disease. Nature. 2001;411(6837):599-603. — doi:10.1038/35079107
Ogura Y, Bonen DK, Inohara N, et al. A frameshift mutation in NOD2 associated with susceptibility to Crohn's disease. Nature. 2001;411(6837):603-606. — doi:10.1038/35079114
Kirsner JB. Historical origins of current IBD concepts. World Journal of Gastroenterology / historical review. — PMC: historical origins of IBD concepts
Dalziel TK. Thomas Kennedy Dalziel 1861-1924. Chronic interstitial enteritis (historical reprint and commentary). — PubMed: 2686949
Van Hootegem P, Pauwels-Coppia M. Is Crohn's disease a rightly used eponym? — PubMed: Crohn disease eponym and priority history
The history of Crohn's disease — Morgagni, Lesniowski, Dalziel, and the 1932 paper. — PubMed: history of Crohn disease / regional ileitis
NOD2/CARD15 and the genetics of Crohn's disease — PubMed: NOD2/CARD15 Crohn disease susceptibility
Mycobacterium avium subspecies paratuberculosis (MAP) and Crohn's disease: the unresolved debate. — PubMed: MAP and Crohn disease
Infliximab and the anti-TNF era in Crohn's disease (history of biologic therapy). — PubMed: infliximab / anti-TNF history in Crohn disease
Crohn's disease versus ulcerative colitis: differentiating the inflammatory bowel diseases. — PubMed: Crohn vs ulcerative colitis / IBD concept
Genome-wide association studies and the polygenic architecture of Crohn's disease. — PubMed: GWAS and Crohn disease risk loci

External Authoritative Resources

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Connections

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