Anticipation phenomenon in familial adenomatous polyposis:an analysis of its origin

AIM To analyze the origin of the anticipationphenomenon,which means earlier death insuccessive generation in familial adenomatouspolyposis.METHODS The study subjects were 2161patients with familial adenomatous polyposisand their 7465 first-degree relatives who weremembers of 750 families registered at ourPolyposis Registry.The ages at death andcumulative mortality rates in the parent,theproband,and the child generations werecompared for both all subjects and the patientsalone.RESULTS In the patients over 5 years of age,the mean age at death was 50.9 years for theparent,42.3 years for the proband,and 33.3years for the child generations,respectively(P【0.001).The deceased rates in the threegenerations were 90.7%,51.3% and 23.1% ofthe patients,respectively,and this differencewas the main cause of the anticipation measuredby parent-child paring method.The cumulativemortality rates for all subjects failed to showanticipation,however the cumulative mortalityrates for the patients showed the anticipation.The anticipation phenomenon was shown by anyparent-child pairing methods for the deceasedpatients.Other important causes of theanticipation were different proportion of causesof death between generations(P【0.001),and alow proportion of detected or deceased patients (P【0.001)in the child generation.CONCLUSION Anticipation in familialadenomatous polyposis may be caused byparent-child paring methods as well as severalintergenerational biases.