Collagenous colitis. Epidemiology, risk factors, clinical presentation and associated autoimmune disorders

Sammanfattning: Collagenous colitis (CC) affects middle-aged women and results in chronic watery non-bloody diarrhoea. The incidence of CC has increased but has never been determined in southern Sweden. During the period 2001-2010 the mean annual incidence was stable; 5.4/105 (median age 71 years). The female: male ratio was 2.8:1, lower than in previous reports. The association between smoking and classic IBD is well known while data on smoking in CC were lacking. Among 116 patients (92 women, median age 62 years) 37% were smokers compared to 17% of controls (p < 0.001). Smokers developed the disease at 42 years (median) compared to 56 years in non-smokers (p < 0.003). Collagenous colitis and LC are regarded as different entities but share many features. Out of 664 patients with CC or LC 65 patients hade been investigated more than once. Conversion occurred in nine (14%, all women, mean age 58 years), three from CC to LC and six from LC to CC. It remains to determine whether this is due to true conversion, spectral disease with varying histology or different histological manifestations over time – the diagnostic criteria could be too vague. Collagenous colitis is associated with autoimmune disorders. This relationship was studied in 116 CC patients (92 women, median age 62 years) and 32% had one or more autoimmune disorder Coeliac disease (13%), autoimmune thyroid disease (10%), Sjögren´s syndrome (3%), diabetes mellitus (2%) and conditions in skin and joints (8%); a pattern of autoimmunity similar to that in classic IBD.