Familial adenomatous polyposis family with clustering of psychiatric disorders.

Familial adenomatous polyposis (FAP) is an inherited disorder that follows an autosomal dominant inheritance pattern and is caused by a germline pathogenic variant in the APC gene. FAP also has extracolonic manifestations, including osteomas, brain tumors, and congenital hypertrophy of the retinal pigmented epithelium. Desmoid tumor is a rare soft-tissue tumor often associated with FAP. APC is a WNT signal transduction molecule that is abundantly expressed in the central nervous system. The truncation mutations of the APC gene are responsible for FAP. Further, the C-terminal domains of APC associate with proteins such as EB1 and hDLG, which are involved in central nervous system functions. In recent years, several reports have indicated an association between FAP and mental disorders. We have identified a family with FAP that has a cluster of mental disorders. The female probrand experienced FAP and desmoid tumors in her thirties. She underwent a total colectomy and tumor resection. Her genetic test revealed a pathogenic germline pathogenic variant in the APC gene, c.3183_3187del. Her maternal grandmother and great-grandmother had colorectal polyposis. She has some mental disorders, and her son and daughter both have autism spectrum disorder (ASD). It was reported that her younger sister and her two daughters have intellectual disability and symptoms of ASD. For these situations, we found that mental health care is crucial when providing genetic counseling and medical care, especially to younger patients with FAP and carriers of pathological variants of the APC gene.