crohn's disease crohn's disease crohn's disease is a type of inflammatory bowel disease (ibd) that may affect any segment of the gastrointestinal tract. symptoms often include abdominal pain, diarrhea (which may be bloody if inflammation is severe), fever, abdominal distension, and weight loss. complications outside of the gastrointestinal tract may include anemia, skin rashes, arthritis, inflammation of the eye, and fatigue. the skin rashes may be due to infections as well as pyoderma gangrenosum or erythema nodosum. bowel obstruction may occur as a complication of chronic inflammation, and those with the disease are at greater risk of colon cancer and small bowel cancer. crohn's diseaseother namescrohn disease, crohn syndrome, granulomatous enteritis, regional enteritis, leśniowski-crohn diseasethe three most common sites of intestinal involvement in crohn's disease (left) compared to the areas affected by ulcerative colitis (colitis ulcerosa, right)specialtygastroenterologysymptomsabdominal pain, diarrhea (may be bloody), fever, weight loss, fatigue, mouth sores, reduced appetitecomplicationsanemia, skin rashes, arthritis, bowel cancerusual onset20 to 30durationlong termrisk factorstobacco smokingdiagnostic methodbiopsy, medical imagingdifferential diagnosisirritable bowel syndrome, celiac disease, behçet's disease, nonsteroidal anti-inflammatory drug enteropathy, intestinal tuberculosismedicationcorticosteroids, biological therapy, immunosuppressants such as azathioprine, methotrexateprognosisslightly increased risk of deathfrequency3.2 per 1,000 (developed world) while the precise causes of crohn's disease (cd) are unknown, it is believed to be caused by a combination of environmental, immune, and bacterial factors in genetically susceptible individuals. it results in a chronic inflammatory disorder, in which the body's immune system defends the gastrointestinal tract, possibly targeting microbial antigens. while crohn's is an immune-related disease, it does not appear to be an autoimmune disease (the immune system is not triggered by the body itself). the exact underlying immune problem is not clear; however, it may be an immunodeficiency state. about half of the overall risk is related to genetics, with more than 70 genes involved. tobacco smokers are twice as likely to develop crohn's disease as nonsmokers. it often begins after gastroenteritis. diagnosis is based on biopsy and appearance of the bowel wall, medical imaging, and description of the disease. other conditions with similar symptoms include irritable bowel syndrome and behçet's disease. there is no known cure for crohn's disease. treatment options are intended to help with symptoms, maintain remission, and prevent relapse. in those newly diagnosed, a corticosteroid may be used for a brief period of time to rapidly improve symptoms, alongside another medication such as either methotrexate or a thiopurine used to prevent recurrence. cessation of smoking is recommended for people with crohn's disease. one in five people with the disease is admitted to the hospital each year, and half of those with the disease will require surgery at some point over a ten-year period. while surgery should be used as little as possible, it is necessary to address some abscesses, certain bowel obstructions, and cancers. checking for bowel cancer via colonoscopy is recommended every few years, starting eight years after the disease has begun. crohn's disease affects about 3.2 per 1,000 people in europe, north america, and the uk. it is less common in asia and africa. it has historically been more common in the developed world. rates have, however, been increasing, particularly in the developing world, since the 1970s. inflammatory bowel disease resulted in 47,400 deaths in 2015, and those with crohn's disease have a slightly reduced life expectancy. it tends to start in adolescence and young adulthood, though it can occur at any age. males and females are equally affected. name the disease was named after gastroenterologist burrill bernard crohn, who in 1932, together with two colleagues at mount sinai hospital in new york, described a series of patients with inflammation of the terminal ileum of the small intestine, the area most commonly affected by the illness. signs and symptoms signs and symptoms crohn's diseaseulcerative colitis defecationoften porridge-like, sometimes steatorrheaoften mucus-like and with blood tenesmusless commonmore common fevercommonindicates severe disease fistulaecommon seldom weight lossoftenmore seldom gastrointestinal an aphthous ulcer on the mucous membrane of the mouth in crohn's disease many people with crohn's disease have symptoms for years before the diagnosis. the usual onset is in the teens and twenties, but can occur at any age. because of the 'patchy' nature of the gastrointestinal disease and the depth of tissue involvement, initial symptoms can be more subtle than those of ulcerative colitis. people with crohn's disease experience chronic recurring periods of flare-ups and remission. the symptoms experienced can change over time as inflammation increases and spreads. symptoms can also be different depending on which organs are involved. it is generally thought that the presentation of crohn's disease is different for each patient due to the high variability of symptoms, organ involvement, and initial presentation. perianal perianal discomfort may also be prominent in crohn's disease. itchiness or pain around the anus may be suggestive of inflammation of the anus, or perianal complications such as anal fissures, fistulae, or abscesses around the anal area. perianal skin tags are also common in crohn's disease, and may appear with or without the presence of colorectal polyps. fecal incontinence may accompany perianal crohn's disease. intestines the intestines, especially the colon and terminal ileum, are the most commonly affected areas of the body. abdominal pain is a common initial symptom of crohn's disease, especially in the lower right abdomen. flatulence, bloating, and abdominal distension are additional symptoms and may also add to the intestinal discomfort. pain is often accompanied by diarrhea, which may or may not be bloody. inflammation in different areas of the intestinal tract can affect the quality of the feces. ileitis typically results in large-volume, watery feces, while colitis may result in a smaller volume of feces of higher frequency. fecal consistency may range from solid to watery. in severe cases, an individual may have more than 20 bowel movements per day, and may need to awaken at night to defecate. visible bleeding in the feces is less common in crohn's disease than in ulcerative colitis, but is not unusual. bloody bowel movements are usually intermittent, and may be bright red, dark maroon, or even black in color. the color of bloody stool depends on the location of the bleed. in severe crohn's colitis, bleeding may be copious. stomach and esophagus the stomach is rarely the sole or predominant site of cd. to date there are only a few documented case reports of adults with isolated gastric cd and no reports in the pediatric population. isolated stomach involvement is very unusual presentation accounting for less than 0.07% of all gastrointestinal cd. rarely, the esophagus and stomach may be involved in crohn's disease. these can cause symptoms including difficulty swallowing (dysphagia), upper abdominal pain, and vomiting. oropharynx (mouth) the mouth may be affected by recurrent sores (aphthous ulcers). recurrent aphthous ulcers are common; however, it is not clear whether this is due to crohn's disease or simply that they are common in the general population. other findings may include diffuse or nodular swelling of the mouth, a cobblestone appearance inside the mouth, granulomatous ulcers, or pyostomatitis vegetans. medications that are commonly prescribed to treat cd, such as anti-inflammatory and sulfa-containing drugs, may cause lichenoid drug reactions in the mouth. fungal infection such as candidiasis is also common due to the immunosuppression required in the treatment of the disease. signs of anemia such as pallor and angular cheilitis or glossitis are also common due to nutritional malabsorption. people with crohn's disease are also susceptible to angular stomatitis, an inflammation of the corners of the mouth, and pyostomatitis vegetans. systemic like many other chronic, inflammatory diseases, crohn's disease can cause a variety of systemic symptoms. among children, growth failure is common. many children are first diagnosed with crohn's disease based on inability to maintain growth. as it may manifest at the time of the growth spurt in puberty, up to 30% of children with crohn's disease may have retardation of growth. fever may also be present, though fevers greater than 38.5 °c (101.3 °f) are uncommon unless there is a complication such as an abscess. among older individuals, crohn's disease may manifest as weight loss, usually related to decreased food intake, since individuals with intestinal symptoms from crohn's disease often feel better when they do not eat and might lose their appetite. people with extensive small intestine disease may also have malabsorption of carbohydrates or lipids, which can further exacerbate weight loss. extraintestinal crohn's disease can affect many organ systems beyond the gastrointestinal tract. complications crohn's diseaseulcerative colitis nutrient deficiencyhigher risk colon cancer riskslightconsiderable prevalence of extraintestinal complications iritis/uveitisfemales2.2%3.2% males1.3%0.9% primary sclerosing cholangitisfemales0.3%1% males0.4%3% ankylosing spondylitisfemales0.7%0.8% males2.7%1.5% pyoderma gangrenosumfemales1.2%0.8% males1.3%0.7% erythema nodosumfemales1.9%2% males0.6%0.7% visual inflammation of the interior portion of the eye, known as uveitis, can cause blurred vision and eye pain, especially when exposed to light (photophobia). uveitis can lead to loss of vision if untreated. inflammation may also involve the white part of the eye (sclera) or the overlying connective tissue (episclera), which causes conditions called scleritis and episcleritis, respectively. other very rare ophthalmological manifestations include: conjunctivitis, glaucoma, and retinal vascular disease. gallbladder and liver crohn's disease that affects the ileum may result in an increased risk of gallstones. this is due to a decrease in bile acid resorption in the ileum, and the bile gets excreted in the stool. as a result, the cholesterol/bile ratio increases in the gallbladder, resulting in an increased risk for gallstones. although the association is greater in the context of ulcerative colitis, crohn's disease may also be associated with primary sclerosing cholangitis, a type of inflammation of the bile ducts. liver involvement of crohn's disease can include cirrhosis and steatosis. nonalcoholic fatty liver disease (nonalcoholic steatohepatitis, nafld) are relatively common and can slowly progress to end-stage liver disease. nafld sensitizes the liver to injury and increases the risk of developing acute or chronic liver failure following another liver injury. other rare hepatobiliary manifestations of crohn's disease include: cholangiocarcinoma, granulomatous hepatitis, cholelithiasis, autoimmune hepatitis, hepatic abscess, and pericholangitis. renal and urological nephrolithiasis, obstructive uropathy, and fistulization of the urinary tract directly result from the underlying disease process. nephrolithiasis is due to calcium oxalate or uric acid stones. calcium oxalate is due to hyperoxaluria typically associated with either distal ileal cd or ileal resection. oxalate absorption increases in the presence of unabsorbed fatty acids in the colon. the fatty acids compete with oxalate to bind calcium, displacing the oxalate, which can then be absorbed as unbound sodium oxalate across colonocytes and excreted into the urine. because sodium oxalate only is absorbed in the colon, calcium-oxalate stones form only in patients with an intact colon. patients with an ileostomy are prone to formation of uric-acid stones because of frequent dehydration. the sudden onset of severe abdominal, back, or flank pain in patients with ibd, particularly if different from the usual discomfort, should lead to inclusion of a renal stone in the differential diagnosis. urological manifestations in patients with ibd may include ureteral calculi, enterovesical fistula, perivesical infection, perinephric abscess, and obstructive uropathy with hydronephrosis. ureteral compression is associated with retroperitoneal extension of the phlegmonous inflammatory process involving the terminal ileum and cecum, and may result in hydronephrosis severe enough to cause hypertension. immune complex glomerulonephritis presenting with proteinuria and hematuria has been described in children and adults with cd or uc. diagnosis is by renal biopsy, and treatment parallels the underlying ibd. amyloidosis (see endocrinological involvement) secondary to crohn's disease has been described and is known to affect the kidneys. pancreatic pancreatitis may be associated with both uc and cd. the most common cause is iatrogenic and involves sensitivity to medications used to treat ibd (3% of patients), including sulfasalazine, mesalamine, 6-mercaptopurine, and azathioprine. pancreatitis may present as symptomatic (in 2%) or more commonly asymptomatic (8–21%) disease in adults with ibd. cardiovascular and circulatory children and adults with ibd have been rarely (<1%) reported developing pleuropericarditis either at initial presentation or during active or quiescent disease. the pathogenesis of pleuropericarditis is unknown, although certain medications (e.g., sulfasalazine and mesalamine derivatives) have been implicated in some cases. the clinical presentation may include chest pain, dyspnea, or in severe cases pericardial tamponade requiring rapid drainage. nonsteroidal anti-inflammatory drugs have been used as therapy, although this should be weighed against the hypothetical risk of exacerbating the underlying ibd. in rare cases, cardiomyopathy, endocarditis, and myocarditis have been described. crohn's disease also increases the risk