Prevalence of inflammatory bowel disease in Japanese psoriatic patients

Psoriatic patients reportedly have a higher prevalence of inflammatory bowel disease (IBD); however, there have been few research studies of Japanese psoriatic patients. To elucidate the prevalence of IBD in Japanese psoriatic patients, a cross-sectional study was performed. Information was collected regarding psoriatic patients with current or prior history of Crohn's disease (CD) or ulcerative colitis (UC) who were treated at Fukuoka University Hospital from 2010 to 2018. Among 681 psoriatic patients (449 men and 232 women), eight (1.2%, six men, two women) had UC and two (0.3%, one man, one woman) had CD. Diagnosis of IBD preceded psoriasis in five patients, while diagnosis of psoriasis preceded IBD in two; the remaining patients' records did not have sufficient information. Seven of 10 UC-positive patients had mild psoriasis, two had moderate psoriasis and one had severe psoriasis. When UC-positive psoriatic patients were compared with IBD-negative psoriatic patients, there were no differences in age at onset of psoriasis, age at first visit or complications (e.g. psoriatic arthritis, hypertension, hyperlipidemia, hyperuricemia and diabetes). However, UC-positive patients had significantly higher body mass index (BMI) (26.7 vs 23.7; P = 0.021), compared with patients without IBD. The CD/UC ratio in this cohort was 0.25, while the prevalence of IBD was 1.2%; these values were both lower than those in previous reports involving Caucasian patients. Patients with psoriasis and UC may have higher BMI and milder skin symptoms than those with psoriasis alone. These observations must be further confirmed by controlled domestic studies with larger samples.