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Multiple Endocrine Neoplasia Type 2
Familial
multiple endocrine neoplasia type 2 (MEN2) is an inherited disorder of the endocrine
glands; these are glands which make and release hormones into the blood stream. MEN2 is
also known as Sipple's syndrome and carries a high risk for the development of a
particular type of thyroid cancer (medullary carcinoma of thyroid or MTC)
What
is the difference between MEN 2A and 2B ?
MEN
2 is classified into three subtypes:
1. MEN 2A
2. Familial medullary
thyroid carcinoma (FMTC)
3. MEN 2B
The
subtypes are distinguished by the different conditions which may arise. MEN 2A and 2B have an increased of developing an
adrenal tumour called phaeochromocytoma. MEN 2A
have a high risk of developing increased parathyroid
activity. Additional features in MEN 2B include mucosal neuromas of the lips and tongue.
This
all sounds very complicated; how is MEN 2 diagnosed ?
The
diagnosis of MEN 2 depends on a combination of clinical findings, family history and
genetic testing.
I
would like to know more about the clinical diagnosis.
1. The diagnosis of
MEN 2A is suspected clinically when two or more specific endocrine tumours (medullary
thryoid cancer, pheochromocytoma or increased activity of the parathyroid gland) occur in
a single individual or in close relatives.
2. Familial Medullary
Thyroid Carcinoma (FMTC) is diagnosed in families with four cases of MTC in the absence of
pheochromocytoma or parathyroid disease.
3. MEN 2B is diagnosed
clinically by the presence of small growths known as mucosal neuromas of the lips and
tongue together with certain other body characteristics associated with medullary thyroid
cancer.
How
common are these conditions ?
It
is estimated that approximately 20 to 25 new cases of MEN 2 occur per year among the 55
million people in the United Kingdom.
MEN
2A consists of 60 - 90 % of MEN 2
FMTC
5 - 35 % of MEN 2
MEN
2 - 5 % of
MEN 2
All
these subtypes seem to be associated with MTC - tell me more…
MTC
originates in the cells of the thyroid gland which manufacture a hormone known as calcitonin. The diagnosis of MTC is suspected in the
presence of an elevated level of calcitonin. A growth arising from the thyroid gland may
be felt in the neck and this may sometimes have spread to lymph glands in the neck or even
to the liver.
What
are the goals in managing this condition?
The
main aims are to
a.
identify
individuals with the relevant mutations associated with MEN 2 before symptoms develop
b.
to
reduce the effects and complications of the disease in those at risk either by screening
for MTC or by prophylactic thyroidectomy
c.
screening
for pheochromocytoma and parathyroid disease before symptoms develop
d.
to
provide appropriate treatment for those who already have tumours
I
have MEN 2 - Will my children get it as well ?
All
MEN 2 subtypes are inherited in an autosomal dominant manner. This means that of
all of your
children, on average, half will carry the gene mutation and be at risk.
The following information may help clarify this further.
· MEN
2A - about 95 % of affected individuals have an affected parent. In the 5% of cases that
are not familial this is due to the development of a new gene mutations.
· FMTC
- multiple family members are affected by definition
· MEN
2B - about 50% of affected individuals have developed
the gene mutations for the first time,
and 50% have inherited the mutation from a parent.
What
methods are available for early detection ?
The
MEN 2 gene has been localized to the long arm of
chromosome 10. Genetic testing for the gene (mutations of the RET proto-oncogene) is available. This identifies
the abnormalities causing the disease in about 95% of individuals with MEN 2A and 2B and
in about 85 % of families with FMTC.
Treatment
will depend on the condition. Follow the links for more details
Phaeochromocytoma
–
surgical removal
Medullary
Thyroid Cancer - surgical removal
Hyperparathyroidism
- surgical
removal
I
have been asked to attend a clinic for Genetic counselling - what is this for ?
Genetic
counselling is the process of providing individuals and their families with information on
the nature, inheritance and implications of genetic disorders in order to help them to
make informed decisions with regard to treatment and other personal decisions.
Prophylactic
(preventive) removal of the thyroid gland with transplantation of the parathyroid glands
is the primary preventive measure for all subtypes of MEN 2. It is safe for all age groups
but the timing of surgery is controversial. In some situations thyroidectomy is performed
as early as five years of age.
What
screening methods are available ?
Annual biochemical screening for phaeochromocytoma in individuals with an identified RET germline mutation is recommended followed by an MRI scan if the results are abnormal. At present this annual screening is recommended until the age of 35 years.
I
would like to learn more: where can I get further information about MEN2?
Links::
www.geneclinics.org/profiles/men2
Patient Support Website
www.mensociety.com
Ó NHS Tayside; 2006; version 1.0
Disclaimer; no liability whatsoever is accepted for information given and all such information, especially with regard to drug usage (UK version provided), must be checked with a person’s health provider.