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Overview of Noonan's
Syndrome
The term Noonan Syndrome
began to be used in 1963 when Dr. Jacqueline Noonan, a paediatric cardiologist,
reported nine children with pulmonary stenosis, short stature, and a characteristic
facial appearance. Noonan Syndrome is a genetic disorder, and is thought
to occur in around 1:1500 people. There is no definitive test for NS as
yet, though about 50% have a mutation at PTPN11, diagnosis is made on
the basis of certain "features". However since these can be
very variable, many of the milder cases may never actually be diagnosed.
Facial Features
- Hypertelorism (widely
spaced eyes)
- Ptosis (droopy eyelids)
- Downward slanting eyes
- Flattened nasal bridge
- Epicanthal folds (excess
skin in the inner corner of the eye)
- Malar hypoplasia (flattened
cheek bones)
- Low set, anteriorly rotated
ears
These features are very variable
however, and the degree to which they are expressed can vary widely not
only from child to child, but also with age. This can add greatly to the
difficulties of diagnosis.
Heart Defects
- Pulmonary valve stenosis
(PS)
- Hypertrophic cardiomyopathy
(HCM)
- Atrial septal defect (ASD)
- Ventral septal defect
(VSD)
Around 80% of babies born
with NS have some sort of heart defect, although many are asymptomatic
and the defect is only discovered when a ‘heart murmur is heard.
The most common heart defect in NS is a narrowed pulmonary valve (Pulmonary
Stenosis), which may also be dysplastic (mis-shaped). Often the narrowing
is not severe and in around 90% of cases surgery is not required. Hypertrophic
cardiomyopathy is also fairly common, causing a thickening of the heart
muscle, often with impaired heart function. However most people with NS
who have HCM remain asymptomatic for many years, and in some cases the
HCM will actually improve with time. An Atrial Septal Defect is an abnormal
opening between the two upper chambers of the heart, resulting in some
improper blood flow from the left to the right side of the heart. Whilst
small ASD’s may close by themselves, surgical closure of larger
defects is often required.
Other Features
- Short stature
- Feeding problems
- Pectus excavatum or carinatum
(indentation or protrusion of the breastbone)
- Broad chest, widely spaced
nipples
- Learning difficulties
- Undescended testes
- Webbed neck
- Low posterior hairline:
hair may be sparse, but is often coarse and curly.
- Bruising and bleeding
- Muscular and skeletal
anomalies
Although approximately 80%
of those with NS will have short stature, that shortness is not normally
extreme: the average male height is 5’5", and the average female
height 5 feet. As babies and children, individuals with NS tend to lie
on or around the 3rd centile on growth charts. Growth Hormone (GH) therapy
has been used to treat some children and adolescents with Noonan Syndrome;
but most children with NS are not actually GH deficient, and although
treatment with synthetic GH increases the rate of growth in early childhood,
it is not know if the therapy actually increases adult height.
Feeding Problems are very
common, particularly in infancy. Babies often have a weak sucking reflex
and tend to tire easily during feeding. Some may show little or no interest
in feeding at all, and tube feeding may be necessary. Frequent and forceful
vomiting is also very common, and difficulties may persist well into the
second year. There may also be problems with weaning, but in general the
feeding problems tend to improve with time.
Learning Difficulties and Mental Retardation. Whilst the majority of individuals
with Noonan Syndrome have IQs that fall within the ‘normal’
range, approximately a third will have learning disabilities and around
10% will require significant special education. But severe ‘mental
retardation’ is actually quite uncommon.The most common learning
difficulty seen in children with Noonan Syndrome is difficulty in verbal
reasoning, although the majority will attend normal schools. No specific
behavioural pattern has been identified, although individuals with NS
often show signs of clumsiness, stubbornness, and irritability. Physical
Development. Infants and children with Noonan Syndrome may present with
developmental delays, and developmental milestones tend to be reached
at a later than average age. For example, the average age at which an
infant with NS can sit alone is 10 months, walk at 21 months, and talk
at 31 months.
Around 60% of boys with NS will have undescended testes, although early
surgical treatment can help prevent problems with fertility. Puberty may
be delayed in both boys and girls, on average reaching puberty around
2 years later than their peers. But although the delay in going into puberty
may cause emotional concerns for the children involved, it also means
that the bones are later in reaching their adult state and so growth may
continue for longer. Females with Noonan Syndrome generally have normal
menstrual cycles and fertility, but in males some decreased fertility
has been observed.
Bruising and Bleeding. Despite the fact that around 65% of children with
NS bruise easily, only around 20% have an actual bleeding disorder. The
most common of these disorders found in NS are Factor XI deficiency, von
Willebrand disease and thrombocytopenia. It has been suggested that individuals
with Noonan Syndrome be evaluated for bleeding disorders prior to surgery,
and if a bleeding disorder is detected precautions should be taken.
Hearing and Speech. Mild hearing loss occurs in up to 40% of individuals;
this is most often the result of recurrent ear infections or glue ear.
However around 3% will experience more serious hearing loss and require
the use of hearing aids. Any hearing impairment may also result in speech
delay.
The Eye/Vision. Nearly all individuals with Noonan Syndrome have some
associated eye abnormalities, the most common of which are:
- hypertelorism (widely
spaced eyes)
- ptosis (droopy eyelids)
- strabismus (cross eyes)
- epicanthal folds (folded
skin in inner corner of eye)
- down-slanting eyes
- amblyopia (reduced vision)
Many of these contribute
to the characteristic facial appearance seen in Noonan Syndrome and do
not usually cause vision problems. However up to 50% of individuals with
NS will require prescription glasses. Although ptosis and strabismus are
not usually severe, in some cases Surgery may be required.
The Lymphatic System. Many individuals with Noonan's have excess skin
around the neck. This appears as a webbed neck, which may have been caused
by a cystic hygroma (a fluid filled area at the back of the neck) developing
during pregnancy. This may be detected by ultrasound examination during
pregnancy, although the presence of a cystic hygroma does not give a firm
diagnosis of Noonan Syndrome. Lymphoedema, or swelling of the hands and
feet, due to an accumulation of lymphatic fluid, is common in new-borns
with NS. The swelling usually diminishes with age. Other problems widely
mentioned within parent groups but not generally mentioned in the literature
include:
- Frequent night-time leg
cramps
- Persistent problems with
constipation
- Difficulty in getting
young children to take enough fluids
- Night sweats
The causes of these problems
are not known and indeed in fact many professionals do not even recognise
that they exist. But at NS conferences in the US and the UK, over 200
families were consulted and of these nearly all suffered from one or more
of the above problems. And whilst they may not be medically important,
they can be very serious problems to the families concerned.
OCCURRENCE AND GENETICS
Because of the problems with diagnosing Noonan Syndrome and the fact that
many of the milder cases may go undiagnosed, estimates of the frequency
of NS vary from between 1:1000 to 1:5000 The condition affects males and
females equally, and a family history is reported in around 50% of cases.
It is recognised that more than one gene may cause Noonan Syndrome, but
a gene for NS has been mapped in some families on the long arm of chromosome
12. The gene for NS is dominant, since an abnormality in either one of
the pair of genes will give rise to the disorder. An affected individual
has one normal and one altered gene, and therefore has a 50% chance of
passing Noonan Syndrome on to each of their children. But as a result
of variable expression, children with NS may have either more or less
severe characteristics than their parents.
FINDING OUT MORE
The Noonan Syndrome Support Group
The Noonan Syndrome Support Group is an international organisation offering
support, information and friendship. Based in the United States, TNSSG
has members from all over the world, including Europe, Australasia, South
Africa, and the rest of the Americas. You can contact them at:
The Noonan Syndrome Support Group Inc., PO Box 145, Upperco, MD 21155,
USA, Tel: 410-374-5245
Their website has lots of valuable information and many contributors worldwide.
They also host chat sessions and have email discussion groups.
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Features
& Anomolies associated with me...
There
are many possible anomalies associated with Noonan's Syndrome (see
a full list here). But here's the main points of the anomalies that
apply to me:
- mild
scoliosis
- prominent/barrel
rib cage
- hyperextendible
joints
- osteoporosis
- short
stature
- broad
forehead
- small
chin
- webbed
neck (posterior cervical hygroma)
- lymphedema
- slightly
wide set & down slanting eyes
with mild drooping eyelids (ptosis)
- edema
- low
posterior hairline
- tendency
toward abnormal development of outer skin layer...things like warts,
skin growing out in little bubble type things, keloids, overdevelopment
of calouses & for me particularly psoriasis
- bruise
very easily (but don't have any of the more serious clotting issues)
- extra
bones in my hands and feet, but they never developed into a full extra
finger or toe or anything
- low
set ears, slightly rotated
- lots
of ear infections
- small
mouth (micrognathia) and a high arched palate
- Dental
problems (including baby teeth getting serious cavity issues)
feeding issues as a child
- continued
digestive/intestinal problems as an adult
- Autoimmune
disfunction
- hypothyroidism
-
& (possibly, as we're now investigating) malformations of my brain
and spine
I'll need to continue also to monitor my heart, and be aware & make
doctors aware whenever I have surgery or any anesthetic, that I'm at
risk for Malignant Hyperthermia (which is an abnormal response to anesthesia
causing extreme high temperature).
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