Co-occurrence of Lynch syndrome and juvenile polyposis syndrome confirmed by multigene panel testing.

Through germline multigene panel testing, we discovered the co-occurrence of Lynch syndrome due to a PMS2 mutation and juvenile polyposis syndrome due to a BMPR1A mutation in a young man with synchronous bladder and colorectal cancers and a family history of colorectal polyps. To our knowledge, this is the first report of an individual having these two hereditary colorectal cancer syndromes. This discovery highlights the benefit of multigene testing over traditional stepwise genetic testing, particularly when a clinical presentation suggests more than one underlying genetic cause. This report adds to the growing body of literature of individuals with multiple inherited cancer gene defects being identified thanks to the increasing implementation of multigene panels with next generation sequencing technologies.