Trichorhinophalangeal syndrome (TRPS) comprises TRPS I (caused by a heterozygous pathogenic variant in TRPS1) and TRPS II (caused by a contiguous gene deletion of TRPS1, RAD21, and EXT1). Both TRPS types are characterized by distinctive facial features (large nose with broad nasal ridge and tip and underdeveloped alae; thick and broad medial eyebrows; long philtrum; thin vermilion of the upper lip; and large prominent ears); ectodermal features (fine, sparse, depigmented, and slow-growing hair and dystrophic nails); and skeletal findings (short stature, brachydactyly with ulnar or radial deviation of the fingers, short feet, and early, marked hip dysplasia). TRPS II is additionally characterized by multiple osteochondromas and an increased risk of mild-to-moderate intellectual disability.

APC-associated polyposis conditions include (classic or attenuated) familial adenomatous polyposis (FAP) and gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). FAP is a colorectal cancer (CRC) predisposition syndrome that can manifest in either classic or attenuated form. Classic FAP is characterized by hundreds to thousands of adenomatous colonic polyps, beginning on average at age 16 years (range 7-36 years). For those with the classic form of FAP, 95% of individuals have polyps by age 35 years; CRC is inevitable without colectomy. The mean age of CRC diagnosis in untreated individuals is 39 years (range 34-43 years). The attenuated form is characterized by multiple colonic polyps (average of 30), more proximally located polyps, and a diagnosis of CRC at a later age than in classic FAP. For those with an attenuated form, there is a 70% lifetime risk of CRC and the mean age of diagnosis is 50-55 years. Extracolonic manifestations are variably present and include polyps of the stomach and duodenum, osteomas, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE), benign cutaneous lesions, desmoid tumors, adrenal masses, and other associated cancers. GAPPS is characterized by proximal gastric polyposis, increased risk of gastric adenocarcinoma, and no duodenal or colonic involvement in most individuals reported.