Objectives: It has been suggested that paucicellular lymphocytic colitis (PLC) should be considered to be part of the morphological spectrum of microscopic colitis. The aim of the study was to evaluate whether PLC may be considered to be a true microscopic colitis, and in this case, whether it is a minor form of lymphocytic colitis (LC) or a different entity.
Methods: All incident cases of PLC, LC, and collagenous colitis (CC) during the period 2004-2006 were included. The incidence rate and the clinical, histopathological, and immunological features of PLC were assessed and compared with those of both LC and CC. Immunoreactivities to CD25, c-Kit, and FOXP3 in lamina propria were assessed.
Results: In all, 19 patients with CC, 19 with LC, and 26 with PLC were identified. CD25+FOXP3+ expression was seen only in classical forms of microscopic colitis: 12 of 19 LC, 14 of 20 CC, and none of 20 PLC cases (P < 0.0001). Diarrhea ceased in 21 of the 26 patients, with a decrease in the daily stool number from 5.08 +/- 0.44 to 1.7 +/- 0.2 (P < 0.005). The five patients with no response to therapy fulfilled the Rome II criteria of irritable bowel syndrome (IBS).
Conclusions: The incidence rate of PLC, identified using objective histological criteria, was higher than those of CC and LC. The lack of expression of CD25+FOXP3+ cells in PLC, in contrast to those seen in both LC and CC, would suggest the existence of different pathophysiological mechanisms and does not support that PLC is a minor form of LC.