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Symptoms
By Mayo Clinic staff
Facial features
The way your child's face appears is one of the key clinical features leading to a diagnosis of Noonan syndrome. These features change depending on the age of your child:
- Early infancy. A baby less than 1 month old may have wide-set and down-slanting eyes, low-set ears, a deep groove and wide peaks in the upper lip, a short neck and a low hairline on the back of the head.
- Infancy. An infant may have prominent eyes with a downward slant and thickened lids, and a depressed root of the nose with a wide base and bulbous tip.
- Childhood. There is often a lack of facial expression.
- Adolescence. An adolescent's face is typically wide at the forehead tapering to a pointed chin, the facial features become sharper and the eyes are less prominent, and the neck lengthens to reveal skin webbing or prominent neck (trapezius) muscles.
- Adulthood. When a child with Noonan syndrome reaches adulthood, the crease that runs from the edge of the nose to the corner of the mouth becomes prominent and the skin may be wrinkled and appear transparent.
Heart disease
More than half of people with Noonan syndrome have congenital heart disease, accounting for some of the key signs and symptoms. Pediatric cardiologists may be the first doctors to see children with Noonan syndrome. Some forms of congenital heart disease are more common when associated with this disorder:
- Pulmonary valve stenosis. This is the most common heart problem seen with Noonan syndrome. Pulmonary valve stenosis is a narrowing of the pulmonary valve, the flap of tissue that separates the lower right chamber (ventricle) of your heart from the artery that supplies blood to the lungs (pulmonary artery). The defect may occur by itself, or there can be additional associated defects.
- Hypertrophic cardiomyopathy. This is abnormal growth or thickening of the heart muscle that affects as many as 30 percent of people with Noonan syndrome.
- Structural defects. People with Noonan syndrome often have structural defects of the heart. The defects involve a hole in the wall that separates the two lower chambers of the heart (ventricular septal defect), or a condition that causes a narrowing of the arteries that carry blood to the lungs for oxygen (pulmonary artery stenosis).
Growth issues
Your child's birth weight will likely be normal, but some children have difficulty with feeding, which can cause poor weight gain until about 18 months. The growth spurt that's usually seen during adolescence may be delayed in your child, but because this disease causes bone maturity to be delayed, your child has the potential to continue growing into his or her 20s. By adulthood, about one-third of people with Noonan syndrome have normal height, but short stature is more common.
Musculoskeletal issues
An unusually shaped chest often with a sunken sternum (pectus excavatum) or raised sternum (pectus carinatum) often occurs in those with Noonan syndrome. Wide-set nipples and a short neck, often with extra folds of skin (webbed neck), also are common. Low muscle tone also may be present.
Learning disabilities
Many children with Noonan syndrome get along without difficulty in school — significant mental retardation is uncommon. About one-third of those with Noonan syndrome may have mild mental retardation. Still, it's not uncommon for people with Noonan syndrome to go on to college, and some have earned advanced degrees.
Eye problems
Nearly all people with Noonan syndrome have abnormalities of their eyes and eyelids. Differences in the shape and size of the eyes are hallmark features. Often the iris is pale blue or green. Problems with the eye muscles (strabismus, or crossed eyes), refractive problems — astigmatism, nearsightedness (myopia), hypermetropia, rapid movement of the eyeballs (nystagmus) and problems with the nerves of the eyes are common.
Bleeding
Most people with Noonan syndrome have a history of abnormal bruising or bleeding. Sometimes the bleeding problem isn't discovered until a person has surgery and experiences excessive bleeding (hemorrhage).
Lymphatic problems
Noonan syndrome can cause problems with the lymphatic system, which drains excess fluid from the body and helps fight infection. These problems can show up before or after birth and can be focused in a particular area of the body or may be widespread. The most common problem is excess fluid (lymphedema) on the back of the hands or top of the feet.
Genital and kidney problems
Many people, especially males, with Noonan syndrome can have problems with the genitals and kidneys. Kidney problems are generally mild and occur in a fairly small number of people with the syndrome. Puberty may be delayed in both boys and girls, but most females usually develop normal fertility. In males, however, fertility may not develop normally — often because of undescended testicles, a condition that's common in males with Noonan syndrome.
Skin problems
Various problems that affect the color and texture of the skin are common. There's also a tendency to develop thick scars after surgery. People with Noonan syndrome often have curly, coarse hair, or sparse hair.
When to see a doctor
The signs and symptoms of Noonan syndrome can be subtle. If you suspect you or your child may have the disorder, see your primary care physician or your child's primary care pediatrician. He or she may then refer your child to a pediatric geneticist or a pediatric cardiologist. Noonan syndrome can be detected with molecular genetic testing. If your unborn child is at risk because of a family history of Noonan syndrome, prenatal tests may be available.
- Noonan syndrome. Genetics Home Reference. http://ghr.nlm.nih.gov/condition=noonansyndrome. Accessed Oct. 22, 2008.
- Learning about Noonan syndrome. National Human Genome Research Institute. http://www.genome.gov/25521674. Accessed Oct. 22, 2008.
- Allanson JE. Noonan syndrome. American Journal of Medical Genetics. 2007;145C: 274-279.
- Allanson JE. Noonan syndrome. GeneReviews. http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=noonan. Accessed Oct. 22, 2008.
- Lin AE. Adults with genetic syndromes and cardiovascular abnormalities: Clinical history and management. Genetics in Medicine. 2008;10(7):469-494.
- DeLuca A. NF1 gene mutations represent the major molecular event underlying neurofibromatosis-Noonan syndrome. The American Journal of Human Genetics. 2005;77(6):1092-1011.
- Tullu MS. Neurofibromatosis-Noonan syndrome or LEOPARD syndrome? A clinical dilemma. Journal of Postgraduate Medicine. 2000;46(2):98-100.
- Hoecker JL (expert opinion). Mayo Clinic, Rochester, Minn. Oct. 23, 2008.
