Chronic Recurrent Multifocal Osteomyelitis Associated with Chronic Inflammatory Bowel Disease in Children

Chronic recurrent multifocal osteomyelitis(CRMO) is a rare disease of children characterized byaseptic inflammation of the long bones and clavicles. Noinfectious etiology has been identified, and CRMO has been associated with a number of autoimmunediseases (including Wegener's granulomatosis andpsoriasis). The relationship between CRMO andinflammatory bowel disease is poorly described. Throughan internet bulletin board subscribed to by 500pediatric gastroenterologists, we identified sixinflammatory bowel disease patients (two with ulcerativecolitis, four with Crohn's colitis) with confirmed CRMO. In all cases, onset of the bony lesionspreceded the onset of bowel symptoms by as much as fiveyears. Immunosuppressive therapy for the bowel diseasegenerally resulted in improvement of the bone inflammation. Chronic recurrrent multifocalosteomyelitis should be considered in any inflammatorybowel disease patient with unexplained bone pain orareas of uptake on bone scan. CRMO may be a rareextraintestinal manifestation of inflammatory bowel disease;alternatively, certain individuals may be geneticallypredisposed to the development of bothdiseases.     

The Dilemma of Chronic Recurrent Multifocal Osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare idiopathic inflammatory disease that affects mainly children and young adults, resulting in significant morbidity especially if not diagnosed early. The clinical signs and symptoms are nonspecific, with a consequential delay in diagnosis. Radiological and histopathological criteria are important for its definition. Two cases of CRMO are reported, highlighting the diagnostic challenge and demonstrating the importance of timely investigations.     

Ulcerative colitis associated enteritis: is ulcerative colitis always confined to the colon?

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon whose etiology is unknown. Small bowel involvement in UC is extraordinarily rare, and should make the clinician question the diagnosis. However, we present a case of a 38-year-old man with voluminous diarrhea following colectomy for well-documented UC; he was found to have ulcerative enteritis with histologic features identical to UC. Also, for the first time, we present an inclusive review of another 11 cases of UC associated enteritis (UCAE) reported in the literature, and discuss the significance of the entity. We conclude that UC is rarely accompanied by enteritis that is distinct from Crohn disease, frequently presents shortly after colectomy, and usually is responsive to traditional therapies for inflammatory bowel disease (IBD).     

Association of chronic non-bacterial osteomyelitis with Crohn’s disease but not with CARD15 gene variants

Chronic non-bacterial osteomyelitis (CNO) is an inflammatory, non-infectious disorder of the skeletal system with unknown etiology. Besides bone-inflammation, patients may present with inflammatory involvement of other tissues. Chronic recurrent multifocal osteomyelitis (CRMO) is the most severe form of CNO. We describe the occurrence of Crohn’s disease (CD) in four patients, previously diagnosed with CRMO. Mutations in CARD15, encoding the NOD2 protein, have recently been found in patients with CD. Based on the occurence of CNO and CD in these four and several reported patients, we hypothesized that CD and CRMO might share a common autoinflammatory process. Thus, we searched for CD associated CARD15 gene variants R702W, G908R and 1007fs in 29 CNO patients, 4 of them additionally diagnosed with CD. In the latter one out of the four showed compound heterozygosity for the gene variants R702W and 1007fs. The allele frequency in the 25 patients diagnosed with CNO but not CD was not different from that already reported in healthy people (R702W 4.0%, G908R 2.0%, 1007fs 2.0%). The occurrence of non-bacterial bone inflammation and granulomatous intestinal inflammation seems to represent an extended phenotype of CD, which partly might be explained by potential disease causing mutations in CARD15. However, CNO without intestinal inflammation is not associated with common CARD15 gene variants. Therefore, other variants of genes coding for proteins involved in innate immunity and inflammation might predispose for the occurrence of CNO.     

Current Understanding of the Pathogenesis and Management of Chronic Recurrent Multifocal Osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is an inflammatory disorder that primarily affects children. Its hallmark is recurring episodes of sterile osteomyelitis. The clinical presentation is insidious onset of bone pain with or without fever. Laboratory studies typically reveal nonspecific evidence of inflammation. Radiologic imaging and histologic appearance resemble those of infectious osteomyelitis. There is a strong association with inflammatory disorders of the skin and intestinal tract in affected individuals and their close relatives, suggesting a shared pathophysiology and supporting a genetic component to disease susceptibility. Two genetic syndromes have CRMO as a prominent phenotype—Majeed syndrome and deficiency of the interleukin-1 receptor antagonist—and suggest that interleukin-1 may be a key cytokine in disease pathogenesis. This review briefly summarizes the main clinical and radiologic aspects of the disease and then focuses on genetics and pathophysiology and provides an update on treatment.     

Die chronische rekurrierende multifokale Osteomyelitis in Assoziation mit chronisch entzündlichen Darmerkrankungen: Die enteropathische CRMO

The enterogenic reactive arthritides and entheropathic spondyloarthropathies are well-known entities. The so-called gut iteropathy concept offers an interesting working hypothesis to link the gut inflammation and the lymphocytic infiltration of the synovium. However, the association of rheumatic diseases belonging to the entity of the SAPHO syndrome with inflammatory bowel diseases (IBD) has only been rarely described in the literature. Among 138 cases of our (heterogenic) SAPHO cohort, we detected 5 patients (1 male, 4 females) with a proven association of SAPHO syndrome with IBD (in 4 cases Crohn's disease, in 1 case ulcerative colitis). Two patients belonged to the juvenileadolescent form and 3 to the adult form of SAPHO syndrome. In all cases the underlying osteoarticluar disease was classified as chronic recurrent multifocal osteomyelitis (CRMO), 2 of them presenting as inflammatory anterior chest wall syndrome. There was a strong association with psoriatic pustular dermatitis. Thus, we present 5 cases of "enteropathic CRMO" demonstrating several analogies to the enteropathic spondyloarthropathies. Both disease entities have in common i) metachronic development with osteoarticluar manifestations often preceding the gastrointestinal disease; ii) Crohn's like lesions that may develop from the stomach to the colon; iii) concomittent or intermittent skin pustulosis which mostly resolves; iiii) the gastrointestinal disease that often dominates the whole syndrome namely in the longterm follow-up. We suggest to transfer the hypothesis of the gut-synovium axis of enteropathic spondyloarthropathies to the entity of CRMO. This concept offers an opportunity to link the target organs gut mucosa, bone marrow and the skin via homing of antigen specific lymphocytes. This concept may help to better understand the pathogenesis of the "Skibo" (i. e., skin-bone) disease CRMO.     

Inflammatory bowel disease is not a risk factor for cardiovascular disease mortality: results from a systematic review and meta-analysis

OBJECTIVES: Inflammation in general, and C-reactive protein (CRP) in particular, are closely associated with atherosclerosis. Similarly, the risk of cardiovascular (CV) disease is increased in several systemic inflammatory diseases. The purpose of this study was to examine whether inflammatory bowel disease (IBD) increases CV mortality, an indirect surrogate for CV disease incidence. METHODS: A systematic review of studies on CV mortality rates in patients with IBD published between 1965 and 2006 was performed. Studies were included for analysis if they reported data on CV-disease-specific standardized mortality ratios (SMRs) for Crohn's disease (CD) and/or ulcerative colitis (UC). A meta-analysis of SMRs from included studies was performed. RESULTS: The review ultimately included 11 studies. Overall there were 4,532 patients with CD and 9,533 patients with UC. SMR point estimates ranged from 0.7 to 1.5 for patients with CD and 0.6-1.1 for patients with UC. There was not a statistically significant increase in CV SMR for either CD or UC in any study. However, two studies demonstrated a statistically significant decrease in CV SMR for UC. Finally, the meta-SMR for CD was 1.0 (95% CI 0.8-1.1) and the meta-SMR for UC was 0.9 (95% CI 0.8-1.0). CONCLUSIONS: IBD is not associated with increased CV mortality. Although CV mortality is a suboptimal surrogate for CV disease incidence, this finding provides indirect evidence against an association between IBD and CV disease.     

Das SAPHO-Syndrom: Klinisch-rheumatologische und radiologische Differenzierung und Klassifizierung eines Krankengutes von 86 Fällen

Synovitis (inflammatory arthritis), acne (pustulosa), pustulosis (psoriasis, palmoplantar pustulosis), hyperostosis (acquired), and ostitis (bland osteomyelitis) are symptoms forming the acronym SAPHO, which is a syndrome of nosologic heterogeneity. All entities forming the SAPHO syndrome are connected by a non-obligate dermatoskeletal association with an aseptic pustulous character. 86 cases were analyzed clinically, radiologically and by histology/histopathology. 31 adult patients showed the typical triad of pustulosis palmo-plantaris (psoriatica, PPP), sterno-costo-clavicular hyperostosis (SCCH), and "productive" spondylopathy, which we define as entity I. spondarthritis hyperostotica pustulopsoriatica (Spond.hyp.pp). Twelve adolescent and 13 adult patients showed entity no. II: chronic recurrent multifocal osteomyelitis (CRMO), being characterized by non-purulent osteomyelitis of plasma-cell sclerotic type, potentially being a reactive inflammatory process. 50% of the adult patients with CRMO showed PPP. Differentiation between these two entities is possible by detection of ossifying enthesiopathy in cases of Spond. hyp.pp and primarily chronic osteomyelitis in cases of CRMO. Two more entities or abortive forms of group I and II are III: the inflammatory syndrome of the anterior chest-wall (ACW syndrome) and IV: the more productive form of isolated sterno-costoclavicular hyperostosis (SCCH). Both are connected quite frequently to HLA-B-27-independent forms of spondarthritis and to pustulous dermatosis. More rarely we find osteo-articular symptoms in cases of acne pustulosa, which form group V: acne-associated spondarthritis and CRMO in the case of acne. Adult forms of CRMO with different forms of appearance (lumosacro-iliac hyperostosis with retroperitobeal fibrosis, pelvic type with affection of the hip-joint) are described. The immunologic theory of a "reactive osteomyelitis" potentially triggered by saprophytes is described. The inverse acne triad is brought in a context of skin symptoms. A case of intercurrent postpartum symptoms together with ulcerative colitis is described. Three cases of patients with Crohn's disease are described. Clinical features, radiological findings, and histopathological elements are brought together to determine the connections between the different entities and the possibilities of differentiation. With these elements together with bone-scan, it is often not necessary to obtain a bone specimen. Therapeutical possibilities, especially concerning CRMO, are discussed. "SAPHO syndrome" is more a sign-post on the way to a more subtle diagnosis when it comes to hyperostotic, skin-associated diseases, and it needs interdisciplinary work to clear the situation.     

Associations of allelic variants of the multidrug resistance gene (ABCB1 or MDR1) and inflammatory bowel disease and their effects on disease behavior: a case-control and meta-analysis study

BACKGROUND: Allelic variants of the ATP-binding cassette, subfamily B member 1 (ABCB1), also known as the multidrug resistance gene (MDR1) that encodes the membrane-bound efflux transporter P-glycoprotein 170 (PGP-170), have been associated with inflammatory bowel disease but with conflicting results. METHODS: The present study examined the association of ABCB1 C3435T and G2677T/A in a large British case-control cohort of 828 Crohn's disease, 580 ulcerative colitis (UC) cases, and 285 healthy controls. The effect of these variants was further examined with respect to phenotypic and epidemiological characteristics. A meta-analysis was carried out of our results and those from 8 previously published association studies of the C3435T variant in inflammatory bowel disease. RESULTS: The 2677T allele was significantly increased in British UC cases compared with controls (45.2% vs. 39.6%; P = 0.034). In particular, the TT genotype was significantly associated with severe UC (odds ratio [OR] 1.90; 95% CI 1.01-3.55) and the use of steroids in UC (OR 1.77; 95% CI 1.08-2.88). No significant association was seen with C3435T and UC, Crohn's disease, or any clinical subgroup. A meta-analysis of 9 association studies of C3435T showed a significant association of the 3435T allele with UC (OR 1.12; 95% CI 1.02-1.23; P = 0.013) but not with CD. CONCLUSIONS: These results indicate that ABCB1 sequence variants are associated with a small increase in the risk of developing UC and may influence disease behavior.     

Chronic non-bacterial osteomyelitis in children

BACKGROUND: Chronic recurrent multifocal osteomyelitis (CRMO) in children is a chronic non-suppurative inflammation involving multiple sites. Some children affected by chronic non-bacterial osteomyelitis (CNO) do not have multiple lesions or a recurrent course. OBJECTIVE: To characterise the long term outcome of children with the full spectrum of CNO. METHODS: 30 children diagnosed with CNO were followed up for a mean of 5.6 years and their disease assessed using a clinical score, multiple imaging, and a diagnostic biopsy, including extensive microbial analysis. RESULTS: 9 patients had unifocal non-relapsing disease, 3 unifocal lesions with relapses, 9 multifocal lesions without relapses, and 9 multifocal lesions with relapses (CRMO). Granulocytes were present significantly more often in CRMO than in unifocal and non-recurrent lesions. Pustulosis was more common in multifocal cases regardless of recurrence. Mean duration of treatment in 15 children with a single occurrence was 9.2 months. Naproxen treatment was generally effective. Naproxen treatment in 12 patients with relapses lasted 25 months. However, 7 of these were not effectively treated with naproxen alone. Five were treated with oral glucocorticoids for 27 days in addition to naproxen, which induced remission in four, lasting for at least 1.5 years. Longitudinal growth of affected bones was not altered, except for the development of hyperostosis. CONCLUSION: CNO is a spectrum of inflammatory conditions, with CRMO being the most severe. Most children with CNO have a favourable outcome of the disease. Oral glucocorticoids may be necessary in severe recurrent cases.     

Long-term evolution and predictive factors of mild inflammatory bowel disease

Background Crohn’s disease (CD) and ulcerative colitis (UC) are potentially progressive diseases. Few data are available on the prevalence and the factors associated with mild inflammatory bowel diseases (IBD). Aim Our aim was to assess the natural history of mild CD and mild UC and to identify predictive factors of mild evolution over the long term. Methods Retrospective study of IBD patients registered in the database of the university hospital CHU of Liège, Belgium. Mild CD was defined as an inflammatory luminal disease (no stricture, abdominal or perianal fistulae) requiring no immunomodulator (IM), anti-TNF and no surgery. Mild UC was defined as no requirement for IM, anti-TNF and no colectomy. Results Four hundred and seventy-three CD and 189 UC were included (median follow-up: 13 and 11 years respectively). At 1 year, 147 patients had mild CD. At 5 years and the maximum follow-up, 56% and 13% patients still had mild CD, respectively. At 1 year, 142 patients had mild UC. At 5 years and the maximum follow-up, 72% and 44% still had a mild UC, respectively. Factors associated with long-term mild CD and UC were older age at diagnosis and absence of corticosteroids in the first year. In UC proctitis location was associated with mild UC. Conclusions In this cohort, 90% of CD patients and 3/4 of UC with mild disease at 1 year lost their mild disease status over time. An old age at diagnosis was predictive of the persistence of a mild CD and UC.     

Does analysis of the antigenic specificities of anti-neutrophil cytoplasmic antibodies contribute to their clinical significance in the inflammatory bowel diseases?

BACKGROUND: The clinical relevance of anti-neutrophil cytoplasmic antibodies (ANCA) in inflammatory bowel diseases is unclear. Definition of their antigenic specificities may improve their diagnostic significance. METHODS: We studied the target antigens of ANCA in 96 patients with ulcerative colitis (UC) and 112 patients with Crohn disease (CD) by indirect immunofluorescence, antigen-specific enzyme-linked immunosorbent assays, and immunodetection on Western blot. We related the presence of antibodies of defined specificity to clinical symptoms. RESULTS: By indirect immunofluorescence, ANCA were present in 58% of UC patients and in 21% of CD patients. Major antigens were catalase, alpha-enolase, and lactoferrin. In UC, ANCA titers correlated with disease activity. In CD, both ANCA, by indirect immunofluorescence, and antibodies to lactoferrin were associated with colonic localization of the disease. Neither ANCA, by indirect immunofluorescence, nor antibodies of defined specificity were associated with duration of disease, use of medication, or a history of bowel resection. CONCLUSIONS: ANCA are useful as markers for UC and colonic localization in CD. Definition of the antigenic specificities of ANCA in inflammatory bowel disease does not significantly contribute to their clinical significance.     

Immunoregulation in the gut: success and failures in human disease

In normal conditions, human gut mucosa is infiltrated with a large number of mononuclear cells. This is a reflection of the fact that human intestine is continuously subjected to a massive stimulation by luminal antigens. This state of "physiological" inflammation is a tightly controlled phenomenon, as several mucosal cells interact to generate and maintain an appropriate local immune response. Changes in cell type number and/or function, including the release of soluble mediators, have been associated with the development of chronic inflammatory diseases, such as Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel disease. Evidence also indicates that the type of inflammatory response occurring in the intestine of patients with CD differs from that in UC, and this probably reflects distinct pathways of immune activation. In CD mucosa, a Th1 response with high IL-12 and IFNgamma production prevails, while in UC a humoral immunity appears to be predominant. Despite this, CD and UC share downstream inflammatory events, characterised by high levels of inflammatory cytokines, free radicals, matrix-degrading enzymes and growth factors.     

Cause of death in patients with inflammatory bowel disease

BACKGROUND: Ulcerative colitis (UC) and Crohn's disease (CD) can both result in disease-related mortality. The aim of the present study was to analyze the comorbid medical conditions that contribute to death of patients with inflammatory disease. METHODS: The United States' vital statistics offer the opportunity to study causes of death broken down by primary and contributing secondary conditions. Deaths from UC and CD were retrieved from the 1991-1996 data files of the National Center for Health Statistics. The strengths of individual associations between each comorbid condition and UC or CD were expressed as proportional mortality ratios, adjusted to the age-, gender-, and race-distribution of the general population. RESULTS: Deaths from UC and CD were found to be associated with a similar set of comorbid conditions and complications. Shock, volume depletion, protein/calorie malnutrition, and anemia were the most frequent comorbid conditions in the group of nutritional, fluid, and electrolyte disturbances. Both diseases were frequently associated with peritonitis and septicemia. Lastly, a large number of deaths were associated with complications following medical and surgical interventions. CONCLUSIONS: Deaths due to inflammatory bowel disease appear to be related to complications from multiple medical interventions and surgical procedures. In managing inflammatory bowel disease, the physician must keep in mind the potential for complications that may be associated with aggressive treatment.     

Activated thrombin activatable fibrinolysis inhibitor (TAFIa) is associated with inflammatory markers in inflammatory bowel diseases: TAFIa level in patients with IBD

BackgroundThrombin activatable fibrinolysis inhibitor (TAFI) has been reported to be involved in the pathogenesis and progression of inflammatory bowel disease (IBD). Activated TAFI (TAFIa) attenuates fibrinolysis by cleaving C-terminal lysine residues thus down-regulating plasminogen activation. To date, no reports on TAFIa in IBD have been published.MethodsPlasma levels of TAFIa were measured using a functional assay in 55 consecutive patients with ulcerative colitis (UC) and 50 with Crohn's disease (CD). Associations of TAFIa with disease activity, hemostatic variables and inflammatory markers were assessed.ResultsPlasma TAFIa was higher in CD patients than in those with UC. The disease activity correlated positively with TAFIa levels in the UC group, but not in the CD group. In UC patients, there were positive correlations of TAFIa with white blood cells, C-reactive protein and fibrinogen and an inverse correlation with albumin. In the CD group, a positive correlation was shown for C-reactive protein, fibrinogen and platelet count, while a negative correlation was noted for albumin.ConclusionsThis study is the first to show that TAFIa is increased in CD patients compared with UC and its levels are associated with inflammatory markers in both forms of IBD. These findings fit in the hypothesis that TAFIa may be a marker of active IBD, and in particular of active UC.     

Chronic pancreatitis and inflammatory bowel disease: true or coincidental association?

OBJECTIVE: Several cases of pancreatitis have been described during the course of Crohn's disease (CD) or ulcerative colitis (UC), but many of them were related to either biliary lithiasis or drug intake. We tried to evaluate the clinical and morphological features of so-called idiopathic pancreatitis associated with inflammatory bowel disease and to define their pathological characteristics. METHODS: Chronic idiopathic pancreatitis was diagnosed on the basis of abnormal pancreatograms suggestive of chronic pancreatitis associated with or without impaired exocrine pancreatic function, or pathological examination in patients undergoing pancreatic resection. We found 6 patients presenting with features of chronic idiopathic pancreatitis and UC and 2 patients with CD seen between 1981 and 1996 in three hospital centers of the south of France. A review of the literature has identified 6 cases of pancreatitis associated with UC and 14 cases of pancreatitis associated with CD based on the above criteria. RESULTS: Hyperamylasemia was not a sensitive test since it was present in 44% and 64% of patients with UC or CD. In UC, pancreatitis was a prior manifestation in 58% of patients. In contrast, the pancreatitis appeared after the onset of CD in 56% of the cases. In patients with UC, pancreatitis were associated with severe disease revealed by pancolitis (42%) and subsequent surgery. Bile duct involvement was more frequent in patients with UC than with CD (58% vs 12%) mostly in the absence of sclerosing cholangitis (16% vs 6%). Weight loss and pancreatic duct stenosis were also more frequent in UC than in CD (41% vs 12% and 50% vs 23%, respectively). Pathological specimens were analyzed in 5 patients and demonstrated the presence of inter- and intralobular fibrosis with marked acinar regression in 3 and the presence of granulomas in 2 patients, both with CD. CONCLUSIONS: Pancreatitis is a rare extraintestinal manifestation of inflammatory bowel disease. Chronic pancreatitis associated with UC differs from that observed in CD by the presence of more frequent bile duct involvement, weight loss, and pancreatic duct stenosis, possibly giving a pseudotumor pattern.     

Chronic recurrent multifocal osteomyelitis and psoriasis—A report of a new association and review of related disorders

In summary, we have described two patients with CRMO and psoriasis, and have reviewed the musculoskeletal manifestations associated with pustular eruptions of the palms and soles. In view of the frequent occurrence of PPP in patients with CRMO, we suggest that the occurrence of psoriasis in our two patients is more than coincidence, and that noninfectious, inflammatory lesions of bone may be another musculoskeletal manifestation of psoriasis. This rare association, as well as the association of PPP with disorders associated with new bone formation, may shed new insights on the relatively common finding of periosteal elevation associated with psoriatic arthritis and the occasional severe juxta-articular osteolytic destructive bone lesions seen in psoriatic arthritis.     

Pamidronate treatment of chronic noninfectious inflammatory lesions of the mandible in children

Noninfectious inflammatory lesions of the mandible occur in chronic recurrent multifocal osteomyelitis (CRMO). Diffuse sclerosing osteomyelitis of the mandible (DSOM) is a condition thought to be a localized form of CRMO. Recently, bisphosphonate therapy, and particularly intravenous pamidronate, has been proposed as a treatment for patients with both CRMO and DSOM who do not improve with nonsteroidal antiinflammatory drug treatment. We report our experience using pamidronate in 2 children with chronic noninfectious osteomyelitis affecting the mandible. We describe the clinical and radiographic features and the treatment, side effects, and clinical and radiographic responses. Our experience suggests that pamidronate is an effective second-line therapy.     

Fecal chromogranins and secretogranins are increased in patients with ulcerative colitis but are not associated with disease activity

BackgroundLittle is known of the importance of chromogranins (Cg) and secretogranins (Sg) in ulcerative colitis (UC). We therefore investigated fecal levels of CgA, CgB, SgII and SgIII, and their association with inflammatory activity, disease duration and medical therapy in UC.MethodsAnalyses of CgA, CgB, SgII, SgIII and calprotectin in stool samples from 41 UC patients and 29 healthy controls were performed. Two stool samples, during relapse and remission, respectively, were obtained from each UC patient.ResultsThe levels of fecal CgA and SgII were higher in UC patients with active disease as compared to healthy controls. CgB and SgII were positively correlated with disease duration, but none of the granins were positively correlated with calprotectin, Mayo score, CRP or serum concentrations of TNF in UC patients with active disease. Also UC patients in remission had higher levels of CgA, CgB, SgII, and SgIII as compared to healthy controls. However, levels of fecal CgA, CgB, SgII and SgIII were lower during active disease relative to remission. Moreover, fecal levels of CgA and SgII were higher in UC patients in remission treated with thiopurines than in thiopurine-naïve patients in remission.ConclusionFecal chromogranins and secretogranins are increased in UC but are not associated with disease activity, but seem to increase with duration of the disease. Thus, fecal granins might reflect structural changes associated with chronicity of disease, or medical therapy.     

Smoking and inflammatory bowel disease

It is well established that smoking cigarettes is associated with Crohn's disease (CD) and that non-smoking is associated with ulcerative colitis (UC). Furthermore, there is convincing evidence that smoking cigarettes has a negative effect on the course of CD, and that smoking cigarettes may improve the disease severity or have a 'protective' effect in some patients with UC. Despite these well-described associations, the mechanism by which cigarette smoking affects CD and UC is not known. Researchers have studied the systemic effects, cellular and humoral immune effects, mucosal changes, and the intestinal permeability changes with inflammatory bowel disease (IBD) and smoking. To date, none of these studies adequately explains the observed clinical patterns. It has been assumed that nicotine is the active agent in these associations, but clinical trials of nicotine chewing gum and transdermal nicotine in UC have shown limited benefit, and have been complicated by significant side-effects. Topical delivery systems for nicotine therapy are currently under development and await future clinical trials.