Novel serine/threonine kinase 11 gene mutations in PeutzJeghers syndrome patients and endoscopic management

AIM:To explore mutations in serine/threonine kinase 11(STK11) gene in Peutz-Jeghers syndrome(PJS) with gastrointestinal(GI) hamartomatous polyps.METHODS:Six Japanese PJS patients in 3 families were enrolled in this study.Each of the cases had hamartomatous polyposis in the gastrointestinal tract,including the small intestine,along with mucocutaneous hyperpigmentation.Narrow-band imaging(NBI)-magnification endoscopy was employed to detect microvascular and microsurface irregularities in the GI lesions.NBI magnification findings could be classified into three groups(type A,type B,or type C).Endoscopic polypectomy was performed using double-balloon enteroscopy or colonoscopy.Genomic DNA was extracted from a whole blood sample from each subject.All of the coding exons of STK11 gene,its boundary regions,and the promoter region containing the polymorphic regions were amplified by polymerase chain reaction,and direct sequencing was performed to assess the germline mutations.RESULTS:NBI-magnification endoscopic observation could detect the abnormalities in microvessels and microsurface structures of GI polyps.Overall,we found 5 cases of type A and one case without the examination for the gastric polyps,while there were 4 cases of type B and 2 case of type A for the colorectal polyps.Seventy-nine small-bowel and 115 colorectal polyps over 27 sessions for each were resected endoscopically without significant complications.The only delayed complication included the occurrence of bleeding in a case,and this was successfully managed with hemoclips.Resected polyps contained no malignant components.Based on mutation analysis,all 3 cases in Family I exhibited the +658C>T nonsense mutation in exon 5,which resulted in the production of a truncated protein(Q220X).In Family II,a case had-252C>A and-193C>A in the promoter region.In Family III,a case was found to have the +1062C>G(F342L) mutation in exon 8.CONCLUSION:We found two novel mutations of STK11 in association with PJS.Endoscopic polypectomy of GI polyps in PJS patients appears to be useful to prevent emergency laparotomies and reduce the cancer risk.