[Early diagnosis of familial adenomatous polyposis based on multiple osteomas of the facial skull].

We describe a 21-year-old patient hospitalised because of a dislocated mandibular fracture and accidentally found to have multiple osteomas of the skull. A subsequent gastroenterological examination revealed the presence of multiple polyps in the large intestine, typical of familial adenomatous polyposis. A disease causing germline mutation in the adenomatous polyposis coli gene was identified by molecular genetic analysis. Although extracolonic features such as multiple osteomas, multiple epidermal cysts and desmoids are frequently found, most cases without a family history of familial adenomatous polyposis or colorectal cancer are only diagnosed because of colonic disease manifestations with colorectal cancer already present. This case report strikingly illustrates that in the absence of a family history the presence of extracolonic features allows presymptomatic diagnosis in familial adenomatous polyposis patients before colorectal cancer has developed.