Genetic evidence that Turcot syndrome is not allelic to familial adenomatous polyposis

Abstract

Turcot syndrome (TS) is a rare genetic disease in which brain tumors occur in association with colonic polyposis. Since Turcot's original description in 1959, there have been disagreements about the mode of inheritance as well as the clinical expression of this condition. Some investigators maintain that TS is a phenotypic variant of the autosomal dominant familial adenomatous polyposis (FAP), while others observe that there are clinical differences between TS and FAP, and that the pattern of inheritance of TS is autosomal recessive. The distribution of persons with colonic lesions in a family with a patient of colonic polyposis and a brain tumor, described in this report, favored the recessive hypothesis. In this family, the involvement of the FAP gene on chromosome 5q21-q22 could be excluded by a linkage study using a panel of FAP-linked DNA markers. This finding, which indicates the occurrence of another polyposis gene elsewhere in the genome, will have consequences for the presymptomatic diagnosis of FAP by linked DNA markers. We conclude that TS is a distinct clinical-genetical entity with the triad of atypical polyposis coli, CNS tumors, and a recessive mode of inheritance.

Genetics of primary brain tumors: a review

“…Chromosome 5q has been associated with these three syndromes [65][66][67]. However, other investigators have shown that at least in some cases of Turcot syndrome there is no involvement of the familial adenomatous polyposis gene on chromosome 5q21-q22, and the type of inheritance is autosomal recessive rather than autosomal dominant, as in familial adenomatous polyposis [69]. Also, the p53 mutations observed in two malignant gliomas were not found in germline tissue of two Turcot syndrome patients [70].…”

Diagnosis, surveillance, and treatment strategies for familial adenomatous polyposis

“…Turcot syndrome (TS) was originally described by Turcot in 1959 [68,69]. It is characterized by the development of primary tumors of the central nervous system, such as glioblastoma multiforme and medulloblastoma, along with numerous adenomatous colorectal polyps and colonic adenocarcinoma.…”

Polyposis coli, craniofacial exostosis and astrocytoma: The concomitant occurrence of the Gardner's and Turcot syndromes

“…By using a panel of FAP-linked DNA markers, Tops et al suggested that involvement of the APC gene at chromosome 5q21-q22 in the family of the pre sented patient was very unlikely [22]. However, the marker currently accepted for clinical determina tion of linkage to mutations at the APC locus (D55346) [21] was not part of the markers that Tops et al applied in their study.…”