Congenital Hypertrophy of the Retinal Pigment Epithelium (CHRPE) as a Screening Marker for Familial Adenomatous Polyposis (FAP): Systematic Literature Review and Screening Recommendations.

Purpose: Familial adenomatous polyposis (FAP) has an almost 100% colorectal cancer risk warranting early detection in gene carriers. This study presents congenital hypertrophy of the retinal pigment epithelium (CHRPE) as a highly specific phenotypical marker for FAP that can be used in screening at-risk individuals. Screening recommendations including morphological subclassification were formulated with supporting literature. Methods: A systematic literature review with a comprehensive search strategy was conducted using online databases. Manual searches of bibliographies and reference lists were also performed. Studies meeting inclusion criteria were graded with respect to their hierarchy of evidence and strength of recommendations according to the National Health and Medical Research Council (NHMRC) guidelines of Australia. Results: Almost 4500 participants were analysed across 28 included studies. The mean specificity of CHRPE as a phenotypical screening marker of FAP was 89% (standard deviation (SD); 14) with a mean sensitivity of 79% (SD; 8). The mean prevalence of CHRPE amongst FAP participants; at-risk participants were found to be 76% (SD; 24) and 37% (SD; 21) respectively. Bilateralism and multiple lesion number ≥3 are features highly specific for FAP. Conclusion: CHRPE was found to be a non-invasive, rapid, early phenotypical screening marker of FAP. Clinical recognition further allows increased gene analysis efficiency. The absence of CHRPE alone cannot exclude FAP. Our screening recommendations provide guidance to clinicians on evidence based CHRPE assessment. We would advocate inclusion of ocular examinations as part of a three-pronged approach, along with endoscopy and genetic testing, for efficient, timely FAP assessment in at-risk individuals.