Purpose: Several studies demonstrate an increased prevalence and concordance of inflammatory bowel disease among the relatives of patients. Other studies suggest that genetic influence is over-estimated. The aims of this study are to evaluate the phenotypic expression and the treatment requirements in familial inflammatory bowel disease, to study the relationship between number of relatives and degree of kinship with disease severity and to quantify the impact of family aggregation compared to other environmental factors.
Methods: Observational analytical study of 1211 patients followed in our unit. We analyzed, according to the existence of familial association, number and degree of consanguinity, the phenotypic expression, complications, extraintestinal manifestations, treatment requirements, and mortality. A multivariable analysis considering smoking habits and non-steroidal-anti-inflammatory drugs was performed.
Results: 14.2% of patients had relatives affected. Median age at diagnosis tended to be lower in the familial group, 32 vs 29, p = 0.07. In familial ulcerative colitis, there was a higher proportion of extraintestinal manifestations: peripheral arthropathy (OR = 2.3, p = 0.015) and erythema nodosum (OR = 7.6, p = 0.001). In familial Crohn's disease, there were higher treatment requirements: immunomodulators (OR = 1.8, p = 0.029); biologics (OR = 1.9, p = 0.011); and surgery (OR = 1.7, p = 0.044). The abdominal abscess increased with the number of relatives affected: 5.1% (sporadic), 7.0% (one), and 14.3% (two or more), p=0.039. These associations were maintained in the multivariate analysis.
Conclusions: Familial aggregation is considered a risk factor for more aggressive disease and higher treatment requirements, a tendency for earlier onset, more abdominal abscess, and extraintestinal manifestations, remaining a risk factor analyzing the influence of some environmental factors.
Keywords: Disease severity; Familial aggregation; Treatment requirements.