What is familial adenomatous polyposis?<
/h2> Famil
ial adenomatous polyposis (FAP) is an inherited disorder characterized by c
ancer of the large intestine (colon) and rectum. People with the classic ty
pe of familial adenomatous polyposis may begin to develop multiple noncance
rous (benign) growths (polyps) in the colon as early as their teenage years
. Unless the colon is removed, these polyps will become malignant (cancerou
s). The average age at which an individual develops colon cancer in classic
familial adenomatous polyposis is 39 years. Some people have a variant of
the disorder, called attenuated familial adenomatous polyposis, in which po
lyp growth is delayed. The average age of colorectal cancer onset for atten
uated familial adenomatous polyposis is 55 years.
In people with classic familial adenoma
tous polyposis, the number of polyps increases with age, and hundreds to th
ousands of polyps can develop in the colon. Also of particular significance
are noncancerous growths called desmoid tumors. These fibrous tumors usual
ly occur in the tissue covering the intestines and may be provoked by surge
ry to remove the colon. Desmoid tumors tend to recur after they are surgica
lly removed. In both classic familial adenomatous polyposis and its attenua
ted variant, benign and malignant tumors are sometimes found in other place
s in the body, including the duodenum (a section of the small intestine), s
tomach, bones, skin, and other tissues. People who have colon polyps as wel
l as growths outside the colon are sometimes described as having Gardner sy
ndrome.
A mild
er type of familial adenomatous polyposis, called autosomal recessive famil
ial adenomatous polyposis, has also been identified. People with the autoso
mal recessive type of this disorder have fewer polyps than those with the c
lassic type. Fewer than 100 polyps typically develop, rather than hundreds
or thousands. The autosomal recessive type of this disorder is caused by mu
tations in a different gene than the classic and attenuated types of famili
al adenomatous polyposis.
How common is familial adenomatous polyposis
?
The
reported incidence of familial adenomatous polyposis varies from 1 in 7,00
0 to 1 in 22,000 individuals.
What genes are related to familial adenomatou
s polyposis?
Mutations in the APC gene cause both classic and attenuated familial adenomatous po
lyposis. These mutations affect the ability of the cell to maintain normal
growth and function. Cell overgrowth resulting from mutations in the APC gene leads to the
colon polyps seen in familial adenomatous polyposis. Although most people w
ith mutations in the AP
C gene will develop colorectal cancer, the number of polyps and the
time frame in which they become malignant depend on the location of the mut
ation in the gene.
Mutations in the M
UTYH gene cause autosomal recessive familial adenomatous polyposis (
also called MYH-associated polyposis). Mutations in this gene prevent cells
from correcting mistakes that are made when DNA is copied (DNA replication
) in preparation for cell division. As these mistakes build up in a person'
s DNA, the likelihood of cell overgrowth increases, leading to colon polyps
and the possibility of colon cancer.
How do
people inherit familial adenomatous polyposis?
Familial adenomatous polyposis ca
n have different inheritance patterns.
When familial adenomatous polyposis results from m
utations in the APC gene, it is inherited in an autosomal dominant pattern, which means one
copy of the altered gene in each cell is sufficient to cause the disorder.
In most cases, an affected person has one parent with the condition.
When familial adeno
matous polyposis results from mutations in the MUTYH gene, it is inherited in an autosomal
recessive pattern, which means both copies of the gene in each cell have mu
tations. Most often, the parents of an individual with an autosomal recessi
ve condition each carry one copy of the mutated gene, but do not show signs
and symptoms of the condition.
Famil ial adenomatous polyposis (FAP) is an inherited disorder characterized by c ancer of the large intestine (colon) and rectum. People with the classic ty pe of familial adenomatous polyposis may begin to develop multiple noncance rous (benign) growths (polyps) in the colon as early as their teenage years . Unless the colon is removed, these polyps will become malignant (cancerou s). The average age at which an individual develops colon cancer in classic familial adenomatous polyposis is 39 years. Some people have a variant of the disorder, called attenuated familial adenomatous polyposis, in which po lyp growth is delayed. The average age of colorectal cancer onset for atten uated familial adenomatous polyposis is 55 years.
In people with classic familial adenoma tous polyposis, the number of polyps increases with age, and hundreds to th ousands of polyps can develop in the colon. Also of particular significance are noncancerous growths called desmoid tumors. These fibrous tumors usual ly occur in the tissue covering the intestines and may be provoked by surge ry to remove the colon. Desmoid tumors tend to recur after they are surgica lly removed. In both classic familial adenomatous polyposis and its attenua ted variant, benign and malignant tumors are sometimes found in other place s in the body, including the duodenum (a section of the small intestine), s tomach, bones, skin, and other tissues. People who have colon polyps as wel l as growths outside the colon are sometimes described as having Gardner sy ndrome.
A mild er type of familial adenomatous polyposis, called autosomal recessive famil ial adenomatous polyposis, has also been identified. People with the autoso mal recessive type of this disorder have fewer polyps than those with the c lassic type. Fewer than 100 polyps typically develop, rather than hundreds or thousands. The autosomal recessive type of this disorder is caused by mu tations in a different gene than the classic and attenuated types of famili al adenomatous polyposis.
The reported incidence of familial adenomatous polyposis varies from 1 in 7,00 0 to 1 in 22,000 individuals.
Mutations in the APC gene cause both classic and attenuated familial adenomatous po lyposis. These mutations affect the ability of the cell to maintain normal growth and function. Cell overgrowth resulting from mutations in the APC gene leads to the colon polyps seen in familial adenomatous polyposis. Although most people w ith mutations in the AP C gene will develop colorectal cancer, the number of polyps and the time frame in which they become malignant depend on the location of the mut ation in the gene.
Mutations in the M UTYH gene cause autosomal recessive familial adenomatous polyposis ( also called MYH-associated polyposis). Mutations in this gene prevent cells from correcting mistakes that are made when DNA is copied (DNA replication ) in preparation for cell division. As these mistakes build up in a person' s DNA, the likelihood of cell overgrowth increases, leading to colon polyps and the possibility of colon cancer.
Familial adenomatous polyposis ca n have different inheritance patterns.
When familial adenomatous polyposis results from m utations in the APC gene, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In most cases, an affected person has one parent with the condition.
When familial adeno matous polyposis results from mutations in the MUTYH gene, it is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mu tations. Most often, the parents of an individual with an autosomal recessi ve condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.
What is familial adenomatous polyposis?
Familial adenomatous polypos is (FAP) is an inherited disorder characterized by cancer of the large inte stine (colon) and rectum. People with the classic type of familial adenomat ous polyposis may begin to develop multiple noncancerous (benign) growths ( polyps) in the colon as early as their teenage years. Unless the colon is r emoved, these polyps will become malignant (cancerous). The average age at which an individual develops colon cancer in classic familial adenomatous p olyposis is 39 years. Some people have a variant of the disorder, called at tenuated familial adenomatous polyposis, in which polyp growth is delayed. The average age of colorectal cancer onset for attenuated familial adenomat ous polyposis is 55 years.
In people with classic familial adenomatous polyposis, the num ber of polyps increases with age, and hundreds to thousands of polyps can d evelop in the colon. Also of particular significance are noncancerous growt hs called desmoid tumors. These fibrous tumors usually occur in the tissue covering the intestines and may be provoked by surgery to remove the colon. Desmoid tumors tend to recur after they are surgically removed. In both cl assic familial adenomatous polyposis and its attenuated variant, benign and malignant tumors are sometimes found in other places in the body, includin g the duodenum (a section of the small intestine), stomach, bones, skin, an d other tissues. People who have colon polyps as well as growths outside th e colon are sometimes described as having Gardner syndrome.
A milder type of familial ade nomatous polyposis, called autosomal recessive familial adenomatous polypos is, has also been identified. People with the autosomal recessive type of t his disorder have fewer polyps than those with the classic type. Fewer than 100 polyps typically develop, rather than hundreds or thousands. The autos omal recessive type of this disorder is caused by mutations in a different gene than the classic and attenuated types of familial adenomatous polyposi s.
How common is familial adenomatous polyposis?
The reported incidence of familial adenomatous polyposis varies from 1 in 7,000 to 1 in 22,000 indivi duals.
What genes are related to familial adenomatous polyposis?
Mutations in th
e APC gene cause
both classic and attenuated familial adenomatous polyposis. These mutation
s affect the ability of the cell to maintain normal growth and function. Ce
ll overgrowth resulting from mutations in the APC gene leads to the colon polyps seen in fa
milial adenomatous polyposis. Although most people with mutations in the APC gene will deve
lop colorectal cancer, the number of polyps and the time frame in which the
y become malignant depend on the location of the mutation in the gene.
Mutations in the < span class="geneSymbol" style="FONT-STYLE: italic">MUTYH gene cause autosomal recessive familial adenomatous polyposis (also called MYH-associa ted polyposis). Mutations in this gene prevent cells from correcting mistak es that are made when DNA is copied (DNA replication) in preparation for ce ll division. As these mistakes build up in a person's DNA, the likelihood o f cell overgrowth increases, leading to colon polyps and the possibility of colon cancer.
How do people inherit familial adenomatous polyposis?
Familial adenomatous polyposis can have different inheri tance patterns.
When familial adenomatous polyposis results from mutations in the APC gene, it is inherit ed in an autosomal dominant pattern, which means one copy of the altered ge ne in each cell is sufficient to cause the disorder. In most cases, an affe cted person has one parent with the condition.
When familial adenomatous polyposis result s from mutations in the MUTYH gene, it is inherited in an autosomal recessive pattern, whic h means both copies of the gene in each cell have mutations. Most often, th e parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the co ndition.
< p>