Is there a database to study mutations in IBD or crohn's disease? I want to study the level of mutations in one gene. I googled but could not find the one.
Not sure what you mean by "level of mutations in one gene" but you can try the Open Targets Platform.
You will see the genes linked to IBD or CD according to the known genetic variants available for the association between genes and diseases coming from different data sources e.g. NIHGR EBI GWAS catalog, PheWAS, Genomics England, etc.