Familial juvenile polyposis syndrome with a de novo germline missense variant in BMPR1A gene: a case report.

Background: Juvenile polyposis syndrome (JPS) is a rare autosomal dominant hereditary disorder characterized by the development of multiple distinct juvenile polyps in the gastrointestinal tract with an increased risk of colorectal cancer. Germline mutations in two genes, SMAD4 and BMPR1A, have been identified to cause JPS.

Case presentation: Here, we report a germline heterozygous missense variant (c.299G > A) in exon 3 BMPR1A gene in a family with juvenile polyposis. This variant was absent from the population database, and concluded as de novo compared with the parental sequencing. Further sequencing of the proband's children confirmed the segregation of this variant with the disease, while the variant was also predicted to have damaging effect based on online prediction tools. Therefore, this variant was classified as likely pathogenic according to the American College of Medical Genetics and Genomics (ACMG) guidelines.

Conclusions: Germline genetic testing revealed a de novo germline missense variant in BMPR1A gene in a family with juvenile polyposis. Identification of the pathogenic variant facilitates the cancer risk management of at-risk family members, and endoscopic surveillance is recommended for mutation carriers.