Features of Noonan Syndrome
Features are numerous and vary in the degree of severity between individuals and within families. Individuals do not necessarily exhibit all of these features.
HEART ABNORMALITIES
Heart abnormalities are found in approximately 80% of children with Noonan Syndrome, the most common being:-
Pulmonary Valve Stenosis (PS), a narrowing of the valve which takes blood from the heart to the lungs for oxygenation of the red blood cells. Sometimes the valve is also found to be Dysplastic which means it is thick and irregular in shape.
Hypertrophic Cardiomyopathy (HCM - which used to be known as HOCM) - thickening of the heart muscles, with disorganisation of the muscle cells. The following are other heart defects which may be found.
Atrial Septal Defect (ASD) - a hole between the two upper chambers of the heart.
Ventricular Septal Defect (VSD) - a hole between the two lower chambers of the heart.
FACIAL CHARACTERISTICS
Noonan Syndrome, like many other conditions, has a recognisable facial “look” made up of separate, notable features. This “look” will vary in detail and definition from child to child and few will display all the facial features noted.
While these features are noted on a clinical basis, most children and adults do not display a severe or extraordinary overall look in comparison to the general population. Indeed, many people feel that the features soften and become even less notable with age.
Eyelids
NS children often have a heavy eyelid; this is called Ptosis. In a few cases the eyelid can be so heavy that it obstructs the vision upwards.
Eye shape
The eyes normally appear to be large and rounded with a downwards slope to the eye socket on the outer edge. There are no associated medical problems with this feature.
Spacing of the eyes
The gap between the eyes may be wider and appear flattened. This is called Hypertelorism. There are no associated medical problems with this feature.
Neck
The neck may be shortened in length and have extra folds of skin. These folds are sometimes described as “webbing” on the neck and extend from the rear of the neck on both sides onto the upper shoulder. The overall effect is to give a view of the neck which is substantially wider at the back than the front and makes an acute
slope to the upper shoulder. This may add to the “round shouldered”look which many NS patients have. There are normally no medical problems associated with this feature.
Hair
While coarse and/or curly hair is noted in many reports as a feature of NS it is not always present. However, there is often a low hairline on the back of the neck. There are no medical problems associated with this feature.
Ears
Ears are normally developed but may appear to be set low on the head in relation to normal positioning. Also the ear may appear rotated in placement so that the lobe is more prominently pointing towards the face than normal. There are no associated medical problems.
Palate
A highly arched palate is noted in NS patients and while this, in a few cases, may impede early feeding and/or speech there are no medical problems associated with this feature.
Nose
While many babies have a flat nasal bridge, this normally fills out with age. There are no associated medical problems.
Forehead
Some babies appear to have a prominent or wide forehead. This may be an illusion related to other facial features. There are no related medical problems associated with this.
FEEDING
Feeding problems are common in Noonan Syndrome. Suckling infants often have a weak suck, a tendency to tire easily during feeding, or show little or no interest in feeding. Frequent and forceful vomiting is also common. Difficulties may also persist later during weaning from liquid to solid food. Usually feeding problems improve with time. However some babies may need to be fed by nasogastric tube for a while.
EYE
The most common eye problems found in Noonan Syndrome are short sightedness and a squint. It is important to have your child’s eyes checked before starting school. The problems which occur can usually be corrected by glasses.
GROWTH
Birth weight is usually average in Noonan Syndrome. After birth, growth in height and weight is usually at the lower end of the normal range. Doctors will plot the measurements of height on a growth chart which allows them to assess whether growth is progressing adequately and also to make some estimate of the child’s final height. Some patients with Noonan Syndrome may be given growth hormone treatment to boost their growth. This does not mean that there is a deficiency of growth hormone nor any hormonal imbalance. The growth hormone used now is artificially manufactured and safe from risks of infection. It does however have to be given by regular injections. Studies in the UK have shown that there should be a 2 - 3cm gain in height in the first year of treatment, but longer term studies will be needed to know if this improvement in growth will continue with longer courses of treatment. There was initial concern about growth hormone causing thickening of the heart muscle. However, it has now been shown that this is not so.
HEARING
Hearing problems are found in Noonan Syndrome. They are most commonly due to recurrent middle ear infections and glue ear.
SPEECH
Speech development may be delayed. This is thought to be associated
with early difficulties in feeding.
DEVELOPMENT, BEHAVIOUR AND INTELLIGENCE
The age at which developmental milestones are achieved may be delayed. For example, the approximate age of sitting alone is 10 months and walking unaided 21 months. Around 10% of children with Noonan Syndrome require significant special education. It should be noted that Noonan Syndrome is not usually associated with severe learning difficulties. No specific behavioural pattern has been identified, however individuals have been reported to show signs of clumsiness, stubbornness, and irritability.
PUBERTY
Around 60% of boys with Noonan Syndrome may have undescended testicles. It is important to treat this surgically at an early age. The operation, called orchidoplexy, will bring the testicle down into the scrotal sac and tie it there with a stitch. Studies have shown that there may be reduced fertility in males and this seems to be due to having both testicles undescended. Early surgical treatment aims to avoid this problem.
Puberty may be delayed in both boys and girls. The average age for girls to start periods is around 14.5 years. Although the delay in going into puberty may cause emotional concerns for the children it also means that the bones are later in fusing and so growth may continue for longer.
BRUISING AND BLEEDING
Around 65% of children with Noonan Syndrome will have a tendency to bruise easily, but bleeding difficulties are rare. It has been found in research studies that there is often an identifiable defect in some of the clotting factors in the blood. The most common clotting factor to be involved is Factor XI. Although this is an interesting research finding it does not usually cause any difficulties. However, as a precaution, it is advisable for patients to be kept in overnight for observation after day surgery to ensure there is no post operative bleeding.
LYMPHATIC SYSTEM
Abnormalities of the lymphatic system may be present. Examples of these are excess fluid at the back of the neck (nucha) during pregnancy and swelling of the hands and feet.
JOINTS AND MUSCLES
The sternum (breast bone) may be depressed. This condition, known as pectus excavatum, is common in the general population and does not usually cause any difficulties. Muscle tone may be poor in early childhood and associated with some delay in motor development. Similarly there may be some tendency to motor incoordination or clumsiness, but this will tend to improve with age.
SKIN AND HAIR
Short, sparse hair or thick, curly hair may be found. Dry patches of skin, abnormalities of the hair follicles (keratosis pilaris), and small brown elevated mole-like skin blemishes (naevi) can also be found.
