HLA associations distinguish collagenous from lymphocytic colitis

Microscopic colitis (MC) and its two major forms collagenous colitis (CC) and lymphocytic colitis (LC) are chronic inflammatory gastrointestinal conditions affecting primarily elderly women with a clinical course characterized by recurrent watery diarrhea and abdominal pain (1). Although now recognized as a world-wide problem with a 0.2% prevalence and reported increasing incidence, their etiopathogenesis is still poorly understood. In particular, it is a matter of debate whether CC and LC represents distinct entities, a pathophysiological continuum, or even manifestations of the same disease at different stages (2, 3). A current hypothesis is that both CC and LC result from abnormal immune response to luminal agents in genetically susceptible individuals, although genetic studies have thus far been limited and underpowered (4).