Lymphoid follicles have been suggested to play a role at the early stage of Crohn's disease lesions.
In the small bowel, lymphoid follicles are grouped, forming Peyer's patches, which develop early in fetal life.
|The probability of small bowel involvement increased from 8 to 16 years of age|
|Inflammatory Bowel Diseases|
The patches grow in size and number until puberty, and undergo involution.
In contrast, colonic lymphoid follicles are isolated and undergo little change during life.
As a result, if lymphoid follicles play a role in the occurrence of Crohn's disease lesions, the distribution of ileal and colonic lesions is expected to be altered in small children.
Dr Meinzer and colleagues reviewed medical records of 2 independent cohorts of consecutive pediatric Crohn's disease.
The cohorts included 136 French patients and 55 Swedish patients.
The researchers recorded disease sites and age of onset, and computed the age-dependent probability to develop ileal lesions.
The CARD15/NOD2 genotype was also analyzed when available, in 99 patients.
The research team found that the curves of disease occurrence were significantly different in case of Crohn's disease with or without ileal lesions.
The researchers observed that at the age of 8 years, the probability of small bowel involvement was 0.2 but increased until 16 years of age to 0.6.
The team observed a slightly higher disease occurrence in patients carrying 1 or more CARD15/NOD2 mutations than in wild-type patients.
In addition, the researchers noted that CARD15 mutations influenced the age of onset of ileal disease.
Dr Meinzer's team concludes, “In children, ileal Crohn's disease lesions are delayed compared with colonic lesions.”
“This observation is in agreement with the previously proposed hypothesis of a pathophysiological role of Peyer's patches in ileal Crohn's disease.”
“The rarity of small bowel lesions should be a warning to be cautious when classifying chronic colitis in small children.”