Crohns disease

Crohn’s disease is a chronic inflammatory bowel disease (IBD) that can affect any portion of the gastrointestinal tract, from mouth to anus. The condition is marked by recurrent flare-ups and periods of remission, and its symptoms extend well beyond the digestive system. Although there is no known cure, modern treatments aim to manage inflammation, prevent relapse, and improve long-term quality of life.
Crohn’s disease is characterised by a patchy, transmural pattern of inflammation. It can lead to significant complications such as bowel obstruction, fistula formation, and malabsorption. The disease affects males and females equally, typically beginning in adolescence or early adulthood, though onset may occur at any age. Its prevalence is highest in Europe and North America but has risen steadily in developing regions since the late twentieth century.

Causes and Pathophysiology

The precise cause of Crohn’s disease remains unknown. Current evidence indicates that the disorder arises from a combination of genetic, environmental, microbial, and immunological factors.

• Genetics: Around half of overall disease risk is genetic, with more than seventy associated genes identified.
• Immune response: Crohn’s disease is an immune-mediated disorder in which the gastrointestinal immune system reacts abnormally to microbial antigens. Although immune dysregulation plays a central role, the disease is not considered classically autoimmune, as the immune system does not target self-antigens. Some theories suggest a possible underlying immunodeficiency.
• Environmental factors: Tobacco smoking increases the risk threefold. Episodes of gastroenteritis may precipitate disease onset.
• Microbial interactions: Altered gut microbiota and aberrant host responses to bacterial antigens contribute to persistent inflammation.

Similar conditions such as irritable bowel syndrome and Behçet’s disease can mimic certain features, necessitating careful diagnostic evaluation.

Gastrointestinal Manifestations

Gastrointestinal symptoms are diverse and vary according to the location and severity of inflammation.

• Abdominal pain is a common first symptom, often localised to the lower right abdomen.
• Diarrhoea may be non-bloody or, less commonly, associated with visible bleeding; severe cases may exceed twenty bowel movements per day.
• Abdominal distension, bloating, and flatulence are frequent.
• Ileitis typically produces watery, large-volume stools, whereas colitis leads to smaller, more frequent motions.
• Perianal disease is common; anal fissures, fistulae, abscesses, and perianal skin tags may cause pain or itchiness.
• Upper gastrointestinal involvement occurs in a minority of cases, presenting with symptoms such as dysphagia, odynophagia, upper abdominal pain, or vomiting.
• Oral manifestations include aphthous ulcers, granulomatous swelling, cobblestoning of the mucosa, and fungal infections due to immunosuppressive therapy. Signs of nutritional anaemia such as glossitis or angular cheilitis may also be present.

Isolated gastric Crohn’s disease is exceedingly rare, accounting for less than 0.07% of cases.

Systemic and Extraintestinal Features

Crohn’s disease affects numerous organ systems beyond the gut.

• Skin: Erythema nodosum, pyoderma gangrenosum, and various infectious rashes can occur.
• Eyes: Uveitis may cause blurred vision, photophobia, and eye pain.
• Joints: Arthritis is common during active phases of the disease.
• Blood: Anaemia may arise from chronic inflammation, iron deficiency, or vitamin malabsorption.
• General symptoms: Fatigue, fever, and weight loss are frequent, particularly during acute flare-ups.
• Growth and development: In children, growth failure and delayed puberty may be the first signs of disease.

Complications

Long-standing inflammation can result in significant complications:

• Bowel obstruction due to stricturing.
• Fistulae and abscesses, especially in the perianal region.
• Increased risk of malignancy, including small bowel and colorectal cancers.
• Malabsorption, resulting in micronutrient deficiencies and weight loss.

Regular colonoscopic surveillance is recommended every one to three years starting eight years after disease onset.

Diagnosis and Epidemiology

Diagnosis is based on a combination of clinical assessment, endoscopy, histopathology, imaging, and laboratory tests. Many individuals experience symptoms for years before diagnosis.
The disease affects approximately 3–12 per 1,000 people in Europe and North America, with lower prevalence in Asia and Africa. Mortality directly attributable to Crohn’s disease is low, but life expectancy may be mildly reduced due to complications.

Treatment

Although Crohn’s disease has no cure, treatment strategies aim to control inflammation, maintain remission, and prevent complications.

• Medications:
  • Corticosteroids provide rapid symptom relief during initial flare-ups but are not used long-term.
  • Thiopurines and methotrexate help maintain remission.
  • Biologic agents target specific inflammatory pathways and are used in moderate to severe disease.
• Lifestyle adjustments: Smoking cessation is strongly recommended.
• Nutrition: Specialised diets may help manage symptoms or correct deficiencies.
• Surgery: While used sparingly, surgery may be necessary for strictures, abscesses, fistulae, and cancer. Up to half of patients require surgery within a decade of diagnosis.

Name Controversy and Historical Background

The condition is named after Burrill Bernard Crohn, who, together with Leon Ginzburg and Gordon Oppenheimer, described a collection of cases involving terminal ileal inflammation in 1932 at Mount Sinai Hospital, New York. However, debate persists regarding attribution. Ginzburg and Oppenheimer had undertaken substantial early work on the disease, and some argue that naming the condition after Crohn alone does not reflect their contributions.