Hereditary Mixed Polyposis is a rare hereditary disorder with multiple types of polyps in the colon.
Inheritance: autosomal dominant
Chromosome location: 15q13-q14
Genetic locus: GREM1 (gremlin 1), which belongs to the bone morphogenic protein (BMP) antagonist family; also SCG5
Abnormality: duplication of GREM1
Additional implicated sites:
(1) mutations of BMPR1A at 10q23.2
(2) 6q
The key feature consists of multiple different types of polyps in the large colon:
(1) polyps that show mixed features of hyperplastic and inflammatory polyps. These may resemble juvenile polyp grossly.
(2) serrated adenomas
(3) other adenomas
(4) Peutz-Jegher type polyps
(5) other types of polyps (hyperplastic, prolapse-type)
(6) lymphoid aggregates
The patient is at risk for colon adenocarcinomas arising out of the polyps.
