Earliest Microscopic Features in Crohn's Disease

Macroscopic and Microscopic Characteristics

The disease begins with characteristic small aphthous ulcers that develop specifically over lymphoid follicles in the intestinal mucosa, surrounded by completely normal-appearing adjacent mucosa 1
Basal plasmacytosis is a common feature, found in 62% of CD cases, and is also common in ulcerative colitis (63% in UC) 2
Non-caseating epithelioid granulomas away from areas of ulceration are typical discriminating features of CD 1
More frequently, granulomas are found in children (61%) than adults 3

The European consensus states that epithelioid granulomas are diagnostic for CD, but microscopic features more common in UC include crypt atrophy and villous mucosal surface 2
Focal or patchy chronic inflammation is only diagnostic in untreated adult patients; treatment can alter distribution patterns 5
The patchy nature of involvement means that adequate sampling (minimum of two biopsies from inflamed regions) is essential 5