Inflammatory bowel disease in pediatric and adolescent patients: A biomolecular and histopathological review

Table 1 Montreal and Paris classifications for Crohn’s disease

	Montreal classification		Paris classification
Age at diagnosis	A1	< 17 yr	A1a	< 10 yr
			A1b	10-16 yr
	A2	17-40 yr	A2	17-40 yr
	A3	> 40 yr	A3	> 40 yr
Location	L1	Ileal disease	L1	Distal 1/3 ileum ± limited cecal disease colonic disease ileocolonic disease isolated
	L2	Colonic disease	L2	upper disease
	L3	Ileocolonic disease	L3
	L4	Isolated upper disease	L4
			L4a	Upper disease proximal to ligament of Treitz
			L4b	Upper disease distal to ligament of Treitz and proximal to distal 1/3 ileum
Behavior	B1	Non-stricturing, non-penetrating	B1	Non-stricturing, non-penetrating
	B2	Stricturing	B2	Stricturing
	B3	Penetrating	B3	Penetrating
			B2B3	both stricturing and penetrating
	P	Perianal disease modifier	P	Perianal disease modifier
Growth	Not applicable		G0	No evidence of growth delay
			G1	Growth delay

Table 2 Montreal and Paris classifications for ulcerative colitis

	Montreal classification		Paris classification
Extent	E1	Ulcerative proctitis	E1	Ulcerative proctitis
	E2	Leftsided colitis distal to splenic flexure	E2	Leftsided colitis distal to splenic flexure
	E3	Extensive colitis distal to hepatic flexure	E3	Extensive colitis proximal to splenic flexure
Severity	S0	Clinical remission	E4	Pancolitis, proximal to hepatic flexure
	S1	Mild ulcerative colitis	S0	Never severe
	S2	Moderate ulcerative colitis	S1	Ever severe
	S3	Severe ulcerative colitis

Table 3 Salient histopathological and biomolecular features in pediatric inflammatory bowel disease

Gene	Genetic alterations	Histopathology	Clinical features	Ref.
IL10RA	G141R	IBD-U	Infantile IBD	[48-50]
IL10RB	W159X
NOD2	R702W, G908R, L1007fsinsC	Abnormal Paneth cells, granuloma-poor	L1 CD	[72]
ATG16L1	T300A
NOD2	R702W, G908R, L1007fsinsC		L1 CD,	[81-87]
			Structuring (B2) behavior	[82,83,87]
			Early surgery	[83]
			Growth delay	[83,84]
			Higher disease activity	[83,88]
NOD2	R702W, G908R, L1007fsinsC	Diminished immunohistochemical	L1, L3 CD	[106-108]
		Expression of alpha-defensin in small intestinal Paneth cells
TLRs	TLR-4 Asp299gly		CD, UC	[111]
IRGM	rs4958847		Fistulizing (B3) CD	[135]
ILRL1 and IL33	Upexpression of mRNA		Extensive UC	[138-140,150]
β-defensin	Low gene copy number	Diminished immunohistochemical expression of beta-defensin 2	L2 CD	[104,105]
HBD2
NCF4	Rs4821544 polymorphism		Perianal CD	[157]

IBD: Inflammatory bowel disease; CD: Crohn’s disease; UC: Ulcerative colitis.