We read with interest the articles by Ben-Horin et al [1] and Arias-Loste [2]. Indeed, inflammatory bowel diseases (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), have been recognized for many years now to include a hereditary component. Familial occurrence in IBD is probably expected to be less frequent in Greece compared to Northern Europe and America [3]. According to retrospective studies, first-degree familial clustering of IBD in the Mediterranean area, including Greece, seems to not exceed 7% in adult [4,5] and 8.5% in pediatric cases [6].
We herein present the results of our study aiming to record all IBD cases with familial clustering in our area. Medical records of all IBD patients followed up at the Division of Gastroenterology at the Ioannina University Hospital and the Northwest Greece IBD Study Group, were retrospectively assessed and studied concerning the existence of all other family members with a firm diagnosis of IBD.
A total of 557 patients with IBD were analyzed and 32 families with at least 2 IBD affected members (first- and second-degree relatives) were recorded. Among these 557 patients, 331 were male (59.4%) and 226 female (40.6%). Among male patients, 211 (63.7%) had UC, 75 (22.7%) had CD and 45 (13.6%) had undetermined colitis (IC). Among females, 145 (64.2%) had UC, 64 (28.3%) CD, and 17 (7.5%) IC. Thirty-two families with at least 2 IBD affected members (first- and second-degree relatives) were recorded, totaling 69 patients. Among these families, there were 26 (81.3%) with concordant diagnoses and 6 (18.7%) with disconcordant diagnoses (Table 1).
Table 1 Intrafamilial inflammatory bowel diseases (IBD) in Northwest Greece
This study showed that any type of confirmed inheritance (first- or second-degree relatives) seems to play a role in IBD familial clustering with a crude rate of 12.4% of our IBD cohort. In this IBD cohort, there was a male predominance and a clear increase in familial UC predisposition compared to CD.
The time frame of sequential diagnoses, like a domino effect, in many of these families we described herein, points towards an environmental factor to which all siblings, and probably also their parents, were exposed during the same period of time.
Of interest, we also recorded one familial IBD case of immigrants in our area [7]. Familial IBD in immigrants have rarely been reported and seem to be of exceptional interest towards a better understanding of disease etiopathogenesis and potential risk factors related also to immigration [8]. Immigrant family cases illustrate potential bias in genetically based studies of CD that rely solely on phenotypic expression. Indeed, it seems that many people might have IBD in their genetic background but either they never express it phenotypically or they express it only under special environmental circumstances such as in the immigration land.
It would be of exceptional interest if any other family members could be investigated for any evidence of silent CD at the time of diagnosis of the disease in their siblings [9]. It can be anticipated that systematic familial screening for silent IBD cases following the first family member diagnosis may explain some of the mystery of the familial IBD aggregation.