The clinical and pathological features of hereditary mixed polyposis syndrome: Report of a South African family

Abstract

Background. Hereditary mixed polyposis syndrome is characterised by multiple large-bowel polyps of differing histological types including a mixture of atypical juvenile polyps, hyperplastic polyps and adenomas. Affected individuals are thought to have an increased risk of malignancy, possibly via the juvenile polyposis pathway. Methods. A 51-year-old woman (with a history of a colectomy for polyps during childhood) presented with rectal bleeding. Endoscopy demonstrated small rectal polyps which were hyperplastic on histology. A family tree was drawn up and the three children of the proband underwent flexible sigmoidoscopy. Results. Endoscopic surveillance of the three children revealed
one who had a similar phenotype to the mother. This child underwent colectomy and ileorectal anastomosis. The pathological specimen revealed more than 70 polyps, with
a combination of juvenile retention, hyperplastic, adenomatous and inflammatory polyps. A second child had multiple small hyperplastic polyps, and the third had a normal colon. Although the gene locus for the disorder has been mapped, neither the gene nor the disease-causing mutation has been defined. Conclusion. A rare inherited polyposis syndrome has been identified in a South African family. Where clinical suspicion of
a possible inherited condition exists, investigating at-risk firstdegree relatives confirms the inherited nature of the disease. It is possible to use genetic haplotyping (i.e. with a range of
markers in the area of the gene) to provide statistical risk to immediate relatives and therefore those at highest risk.

South African Journal of Surgery Vol. 46 (3) 2008: pp. 90-92