Collagenous colitis in systemic sclerosis: an overlooked and treatable complication.

Collagenous colitis (CC) is an inflammatory bowel condition of unknown etiology. Systemic sclerosis (SSc) has been associated with CC in a few cases, but it is not clear whether CC could be considered an unusual manifestation of SSc or an independent condition. Here we present a case of SSc-associated CC and compare routine histology and immunofluorescence studies for allograft inflammatory factor 1 and caveolin 1 expression with other cases of CC and healthy controls. All CC biopsies showed characteristic sublaminal collagen accumulation and a decrease of caveolin 1 expression, this latter finding consistent with and common in any fibrotic reaction. In contrast, the expression of allograft inflammatory factor 1 was increased only in the SSc-CC specimen, suggesting a distinct pathogenesis. A literature review revealed 6 previously reported cases of SSc-CC with common clinical features. These observations suggest that CC should be suspected as a rare gastrointestinal complication of SSc and that clinicians should be aware of the possibility in SSc patients developing watery diarrhea.