The value of opthalmic examinations in familial adenomatous polyposis syndrome screening

Abstract

SUMMARY
The dominantly inherited gastrointestinal polyposis
syndromes are divided into adenomatous and hamartomatous
varieties, depending on the histology of the polyps.
The justification for screening as a method of cancer
prevention in inherited gastrointestinal polyposis syndromes
is well established as the cancer risk in FAP patients
presenting with symptoms varies from 32%-57%.
Screening methods in inherited polyposis syndromes
include non-invasive screening methods such as family tree,
clinical examination for extracolonic malignancies, dilated
fundus examination (CHRPE), DNA analysis and APC gene
mutations.Invasive screening methods include endoscopy,
small bowel radiography and fundus angiography.
Congenital hypertrophy of retinal pigment epithelium
(CHRPE) has been reported in association with familial
adenomatous polyposis and Gardner syndrome and the
presence of multiple CHRPE lesions has been correliated
with the presence and development of polyposis in these
conditions. When present, CHRPE is a reliable clinical
marker. In CHRPE-negative families, negative ophthalmic
examinations are of no diagnostic value.
Opthalmoscopy facilitates genetic analysis because the status of CHRPE considerably facilitates locating the
mutation in genetic diagnostics. Thus, the combination of
an ophthalmic examination with a DNA analysis and
endoscopy improves the risk assessment for carriers of
inherited gastrointestinal polyposis syndromes.
Children of affected patients should undergo flexible
proctosigmoidoscopy beginning at 10 to 12 years of age and
repeated every 1 or 2 years until 35 years of age; thereafter
examinations should be performed every 3 years. Because
the age at which colorectal polyps develop varies, screening
by repeated bowel examination is necessary from puberty
until at least 40 years of age before a family member can be
considered unaffected.
Basically, there are two surgical options for patients with
inherited gastrointestinal polyposis syndromes; subtotal
colectomy with ileorectostomy on the one hand, or total
colectomy with pouch-anal anastomosis or terminal
ileostomy on the other.
Key words: FAP (familial adenomatous polyposis), APC gene
(adenomatous polyposis coli), CRC (colorectal cancer),
CHRPE (congenital hypertrophy of retinal pigment
epithelium), inherited polyposis syndromes