TY  - CHAP
M1  - Book, Section
TI  - Inflammatory Bowel Disease
A1  - Babyatsky, Mark W.
A2  - Murray, Michael F.
A2  - Babyatsky, Mark W.
A2  - Giovanni, Monica A.
A2  - Alkuraya, Fowzan S.
A2  - Stewart, Douglas R.
PY  - 2014
T2  - Clinical Genomics: Practical Applications in Adult Patient Care
AB  - Disease  summary:The  inflammatory  bowel  diseases  (IBDs)  are  prototypic  complex  genetic  disorders,  involving  multiple  interacting  genetic  loci  and  environmental  factors  that  trigger  disease.IBD  is  comprised  of  two  inter-related  disorders,  Crohn  disease  (CD),  and  ulcerative  colitis  (UC),  as  well  as  indeterminate  colitis  (IC).  IC  describes  the  5%  to  10%  of  IBD  involving  only  the  colon  and  is  neither  classic  CD  nor  UC.Clinical  presentations  of  UC  and  CD  overlap;  both  present  with  diarrhea,  bloody  diarrhea,  abdominal  pain,  most  extraintestinal  manifestations,  weight  loss,  and  fever.Anatomic  involvement:  CD  can  involve  any  portion  of  the  gastrointestinal  (GI)  tract,  most  commonly  the  terminal  ileum  (5%-75%)  and  colon  (20%-50%).  CD  causes  transmural  inflammation  in  all  four  layers  of  bowel  wall;  extension  through  the  bowel  wall  can  cause  fistulae,  abscesses,  or  perianal  complications.  Strictures  secondary  to  fibrosis  are  relatively  common.  UC  is  localized  to  varying  lengths  of  continuous  inflammation  proceeding  proximally  from  the  rectum;  a  discontinuous  cecal  patch  may  be  present.  UC  is  limited  to  mucosal  and  submucosal  inflammation,  and  does  not  cause  perianal  or  intra-abdominal  disease;  strictures  are  much  less  common  than  in  CD.Differential  diagnosis:Infectious  colitis  (bacterial,  viral,  protozoal),  pseudomembranous  colitis  (Clostridium  difficile  toxin),  and  ischemic  colitisMonogenic  forms:No  single  gene  cause  of  IBD  is  known  to  exist  except  perhaps  for  a  rare  form  of  CD  (see  IL-10  pathway  later).Family  history:An  affected  first-degree  relative  confers  a  relative  risk  of  30  to  40  for  CD  and  10  to  20  for  UC.  Overlapping  risk  occurs  since  first-degree  relatives  of  patients  with  CD  have  relative  risk  of  3.9  for  developing  UC.Twin  studies:Monozygotic  twins  have  a  20%  to  50%  concordance  rate  in  CD,  much  lower  in  UC.Environmental  factors:Luminal  microbes  or  microbial  products  are  implicated  as  “environmental”  triggers  for  IBD.Genome-wide  associations:Many  associations  exist.  Disease-associated  genetic  variants  (single-nucleotide  polymorphisms  [SNPs])  provide  insight  into  disease  pathogenesis;  testing  for  SNPs  is  not  yet  clinically  validated  to  diagnose  or  guide  management  of  IBD.Pharmacogenomics:Testing  for  common  thiopurine  S-methyltransferase  (TPMT)  variants  to  guide  management  has  proven  validity  in  some  clinical  circumstances.  
SN  - 
PB  - McGraw-Hill Education
CY  - New York, NY
Y2  - 2024/04/19
UR  - accessmedicine.mhmedical.com/content.aspx?aid=1102702069
ER  -