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Abstract Familial adenomatous polyposis (FAP) is an autosomal dominant syndrome caused by germline variants in the APC gene, leading to the development of numerous colorectal polyps and significantly increases the risk of colorectal cancer. A diagnosis is typically made using colonoscopy, and genetic testing can assist in patient surveillance and carrier identification. Recent advances include the use of whole-genome array comparative genomic hybridization (a-CGH), which provides better resolution of genetic imbalances. We aimed to explore the specific features of FAP patients with whole APC gene deletions using high-resolution a-CGH and to compare patient characteristics. Two polyposis patients with whole APC deletions were identified, and the lost genetic sizes ranged from 0.3–1.1 Mb. Nervous abnormalities were a characteristic symptom in a patient with a 1.1 Mb loss. A patient with an approximately 0.3 Mb loss, which included the entire APC gene, presented a polyposis phenotype without intellectual disability. The comparison of genetic losses, with or without intellectual disability, revealed 7 genetic changes. Consequently, EPB41L4A is a candidate gene associated with the neurogenic phenotype.

Abstract We report a case of a fetus with short-rib thoracic dysplasia (SRTD) with polydactyly that also presented with atypical severe acro-mesomelic ossification defects. Genetic analysis using massively parallel sequencing of a skeletal dysplasia panel revealed compound heterozygous variants in DYNC2H1. This clinical report highlights the challenges associated with diagnosing the diverse phenotypes in the SRTD group and emphasizes the importance of genetic surveillance with a targeted gene panel for accurate diagnosis.

Abstract A young patient diagnosed with advanced colon cancer and liver metastasis was found to have familial adenomatous polyposis (FAP) through comprehensive genomic analysis. Whole-genome array comparative genomic hybridization (aCGH) revealed germline deletions at chromosome 5q22.1-22.2 encompassing the entire APC gene. The patient and her son exhibited mild intellectual disability without developmental delay. This case highlights the need for further exploration of the characteristics associated with whole APC deletions. aCGH is a valuable tool for studying FAP and provides a detailed analysis of large deletions.