Articular-peripheral complications and axial involvement occur in 23% and 4%, respectively, of IBD adult patients[4]; in this group, 1 out of 5 shows peripheral arthritis, axial arthritis or both[5,6]. Stawarsky et al[7] carried out an epidemiological study on pediatric IBD patients that confirmed IBD-associated arthropathy in 7%-25% of patients. Although in some studies, there was an increased prevalence of arthritis in the pediatric population compared to adults[8], with female prevalence. In a recent retrospective, prospective study, the phenotypic expression of the disease between patients with childhood-onset IBD (133 pediatric patients) and adulthood-onset (179 adult patients) cases was evaluated, observing that EIMs in pediatric age patients were more frequent (14.3% vs 7.3%) and joint involvement had the same incidence (4.1% vs 4.5%)[9]. Lakatos et al[10] have suggested that in 29% of pediatric IBD there was a risk of developing EIMs within a follow-up period of 15 years. Dotson et al[11] examined the rates of EIMs in a pediatric IBD population, and reported the prevalence of arthralgias (17%), followed by aphthous stomatitis (8%) and arthritis (4%). Furthermore, joint symptoms were correlated with severity and activity of intestinal disease. Orchard et al[12] proposed a classification of enteropathic peripheral arthropathies in adults, distinguishing between Type 1 (pauciarticular, large, inferior articulations) and Type 2 arthritis (polyarticular, small, superior articulations). Type 1 arthritis (4%-17% of patients with Crohn’s disease, CD) is correlated with IBD-activity and affects less than five joints (usually ankles, knees, hips, wrists and, sometimes, elbows and shoulders) with evidence of swelling or effusion. Type 2 (2.5% of patients with CD) follows a course independent of the activity of IBD, with persistent symptoms. Type 1 arthritis is more frequent in adult patients with stenosing and penetrating perianal CD, and twice as frequent in patients with colonic and ileocolonic disease, as opposed to patients with ileal disease. Another form of arthritis has been proposed, type 3 peripheral, which includes patients with both axial involvement and peripheral arthritis.
Axial forms are different, with a clinical course generally independent of IBD activity index, and sacroiliitis (SI) may also be asymptomatic in 50% of patients with CD[13,14]. In ulcerative colitis (UC), articular complications are more frequent in patients with pancolitis, as opposed to patients with proctitis or left-sided UC[15].