Pediatric patients with untreated ulcerative colitis may present initially with unusual morphologic findings.

BACKGROUND: Anecdotal observations by the authors of this study, together with the results of a few previous smaller studies, suggest that children with new-onset (previously untreated) ulcerative colitis (UC) may occasionally present with discontinuous disease, relative or absolute rectal sparing, and may lack histologic features ofchronicity. Therefore, the objectives of this study were to determine the clinical and pathologic features of new-onset UC in children and to compare the initial presentation of UC in this group with a control group of adults.

DESIGN: Routinely processed rectal and colonic mucosal biopsies from 73 pediatric (male/female ratio 33/40, mean age 11.5 years, range 2.5-18 years) and 38 adult patients (male/female ratio 15/23, mean age 41.5 years, range 27-64 years) who presented with new-onset UC were evaluated for a variety of clinical and pathologic features, including duration of symptoms prior to presentation, crypt architectural (e.g., atrophy, branching) and nonarchitectural (e.g., basal plasmacytosis, Paneth cell metaplasia) features of chronicity, degree of active inflammation, and distribution and extent of disease.

RESULTS: A significant proportion of children with new-onset UC had patchiness of microscopic features of chronicity (21% of patients), relative (23%), or absolute (3%), rectal sparing, and had little or no crypt architectural distortion in their rectal biopsies (8%). These features were not observed in adult patients with UC. In addition, a higher proportion of children with UC initially presented with subtotal or with pancolitis compared with the adults (42% vs. 11%; P < 0.002).

CONCLUSIONS: A significant proportion of children with new-onset UC may show unusual patterns of disease. Pathologists should be aware of these findings since they have significant implications for the differential diagnosis of pediatric inflammatory bowel disease.