title: Lynch syndrome in Tunisia: first description of clinical features and germline mutations.
abstract: OBJECTIVE
  High rates of early colorectal cancers (CRC) are observed in Tunisia suggesting genetic susceptibility. Nevertheless, up to now, no molecular study has been performed in the Tunisian population. In our research, we evaluated the clinical characteristics of Tunisian families suspected of Lynch syndrome and the contribution of DNA mismatch repair (MMR) genes.
  
  
  METHODS
  Thirty-one unrelated families suspected of Lynch syndrome were studied. Probands were tested for the presence of germline mutations in the MMR genes MLH1, MSH2, MSH6 and in MUTYH. Available tumours were analysed for microsatellite instability and expression of MMR proteins. Detailed family and medical histories were collected.
  
  
  RESULTS
  A total of 134 cancers were noted in the 31 families, the most frequent type of cancer corresponding to CRC (69%), followed by uterine cancer (7.5%). Germline mutations were identified in 11 (35.5%) families (six MSH2, five MLH1, including seven novel mutations), seven of which fulfilled the Amsterdam criteria (sensitivity, 63.6%; positive predictive value, 58.3%). Noteworthy, germline mutations were detected in 52.6% of male patients tested, but in only 8.3% of females (p = 0.02). Moreover, CRC were essentially left sided in families without detected mutation (p = 0.017). Ages of onset of cancers and tumour spectrum were very similar in families with or without MMR germline mutation, contrasting with previous studies performed in other populations.
  
  
  CONCLUSIONS
  MMR genes contribute significantly to CRC susceptibility in the Tunisian population. However, the cause of early CRC susceptibility remains unknown in most cases, especially in women and in patients with early left colon or rectal cancer.
authors.affiliation: Laboratoire de Biochimie et Biologie Moléculaire de Faculté des Sciences de Tunis, Tunis, Tunisia.
authors.forename: Sana Aissi-Ben
authors.initials: SA
authors.lastname: Moussa
authors.forename: Amel
authors.initials: A
authors.lastname: Moussa
authors.forename: Nadia
authors.initials: N
authors.lastname: Kourda
authors.forename: Amel
authors.initials: A
authors.lastname: Mezlini
authors.forename: Nabil
authors.initials: N
authors.lastname: Abdelli
authors.forename: Farid
authors.initials: F
authors.lastname: Zerimech
authors.forename: Taoufik
authors.initials: T
authors.lastname: Najjar
authors.forename: Sarah Ben
authors.initials: SB
authors.lastname: Jilani
authors.forename: Nicole
authors.initials: N
authors.lastname: Porchet
authors.forename: Farhat Ben
authors.initials: FB
authors.lastname: Ayed
authors.forename: Mohamed
authors.initials: M
authors.lastname: Manai
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Buisine
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000328:Adult; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000235:genetics* / Q000473:pathology*; D053843:DNA Mismatch Repair / Q000235:genetics; D005190:Family; D005260:Female; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D010375:Pedigree; D010641:Phenotype; D055815:Young Adult
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein