Mycobacteria and subgroups of patients in Crohn's disease.

Some recent studies have proposed a subclassification of Crohn's Disease (CD) on the basis of the pathological picture. In fact CD is a heterogeneous disease, and it is probable that the clinical and pathological disorders we now consider as CD may in the near future be divided into several conditions, probably with different causes as well, including environmental factors. Clinical and pathological similarities to mycobacterial disease, along with recent isolation of mycobacteria from tissues taken from patients with CD, and the recognition of atypical mycobacteria as causative agents of an enteritis pathologically similar to CD, all go to strengthen the hypothesis that these organisms are one of the above environmental factors. Researchers should therefore seek to identify and characterize this subgroup of CD patients who may have mycobacterial disease and to perform trials of antimycobacterial therapy. Analysis of the literature gives some suggestions for identifying this subgroup of patients: i) isolation of atypical mycobacteria from the tissues; ii) presence of high specific antibody levels and increase of same after antimycobacterial therapy; iii) presence of granulomas, and iv) strong suspicion of an environmental factor.