BACKGROUND Perinuclear antineutrophil cytoplasmic antibodies (pANCA) have been detected in a clinically distinct Crohn's disease subpopulation. Antibodies toSaccharomyces cerevisiae (ASCA) have been demonstrated in the majority of patients with Crohn's disease.

AIMS To examine the relationship between selective marker antibody expression in Crohn's disease and disease onset, location, and clinical behaviour patterns.

RESULTS Using multiple regression analyses, higher ASCA levels were shown to be independently associated with early age of disease onset as well as both fibrostenosing and internal penetrating disease behaviours. Higher ANCA levels were associated with later age of onset and ulcerative colitis-like behaviour. Substratification of the Crohn's disease population using selective ANCA and ASCA expression (high levels of a single marker antibody): (1) distinguished homogeneous subgroups that manifested similar disease location and behaviours; and (2) identified patients with more aggressive small bowel disease.

CONCLUSIONS The findings suggest that by taking into account the magnitude of the host immune response, Crohn's disease can now be stratified on an immunological basis into more homogeneous clinically distinct subgroups, characterised by greater uniformity among anatomical distribution of disease and disease behaviour.