Psoriasis Phenotype in Inflammatory Bowel Disease: A Case-Control Prospective Study

Whether inflammatory bowel disease [IBD] is associated with specific psoriasis phenotypes is undefined. In a case-control prospective study, we aimed to assess the severity and phenotype of psoriasis in IBD vs matched non-IBD controls with psoriasis [non-IBD]. From 2011 to 2013, dermatological assessment was performed in all IBD patients showing lesions requiring characterisation. In patients with psoriasis, assessment included: presence, characteristics, and severity. Each IBD patient with psoriasis was matched [gender, ethnicity, age +/- 5 years] with one non-IBD patient with psoriasis. Statistical analysis: data were expressed as median [range], chi-square, Student's t test. Dermatological assessment was performed in 251 IBD patients [115 females, age 47 [16-85]; IBD duration 9 years [1-46]]: 158 Crohn's disease [CD] [63%], 93 ulcerative colitis [UC] [37%]. Psoriasis was detected in 62 [25%] IBD patients: 36 [58%] CD, 26 UC [42%; p = 0.44]. Clinical characteristics were comparable between IBD patients with or without psoriasis: age 50 [23-72] vs 47 [16-85]; IBD duration 9.5 [1-46] vs 9 [1-41]; p = non-significant]. The non-IBD group included 62 patients with psoriasis: 35 male; age 47 [18-75]. Mild psoriasis was more frequent in IBD vs non-IBD [87% vs 53%; p < 0.0001], whereas moderate and severe psoriasis were more frequent in non-IBD vs IBD [37% vs 13%, p = 0.004; 10% vs 0%; p = 0.036]. Plaque-type psoriasis was the most common phenotype in both IBD and non-IBD [p < 0.0001 vs others phenotypes].The frequency of plaque-type, nail psoriasis and psoriatic arthritis was lower in IBD vs non-IBD [p = 0.008; p < 0.0001; p = 0.006]. Psoriasis occurred after anti-tumour necrosis factor [TNF]alpha treatment in six CD patients [7%]. Severity and phenotypes of psoriasis may differ between patients with IBD and their matched non-IBD controls.