Phenotypes of inflammatory bowel disease in the Māori population of New Zealand.

Background: Māori have historically seen a lower rate of inflammatory bowel disease (IBD) compared to New Zealand's non-Māori population. Recent reports have shown an increasing rate of IBD among Māori patients.

Aim: We performed a study to identify the phenotypes of IBD in the Māori population.

Methods: Patients with IBD of Māori ethnicity were retrospectively identified from four large regions of New Zealand. Electronic records were reviewed to collect details of patients' demographics, phenotypes and clinical features.

Results: We identified 165 Māori patients with IBD, of whom 74 (45.4%) had Crohn disease (CD), 86 (53.5%) had ulcerative colitis (UC) and 5 (3.0%) had IBD-unclassified (IBD-U). There were more female (61.8%) patients compared to male (38.2%). This was attributed to the higher ratio of female patients with CD over male (73.9% vs 26.1%), whereas sex was evenly distributed in UC (female 52.2%, male 48.8%). Ileocolonic CD was most frequently seen (36.2%), and the majority had non-stricturing disease (62.3%) with the absence of perianal involvement (78.2%). Bimodal age peaks were observed, with a first peak at 25-29 years and a second peak at 45-49 years. There was a five-fold increase in the incidence of IBD in Māori over 20 years.

Conclusions: We present the largest study describing IBD in Māori. IBD phenotypes in Māori were similar to previous regional IBD reports, but there was a significantly higher proportion of female patients with CD in Māori and an earlier second age peak at 45-49 years. Increasing incidence of IBD in Māori has again been demonstrated.