It is estimated that 50-80 percent of individuals with Noonan syndrome have a congenital heart defect. The most common heart defect seen is pulmonary valve stenosis, which is a narrowing in the valve attached to the blood vessel that carries blood out of the heart to the lungs. Other types of congenital heart defects are also seen in patients with Noonan syndrome, including septal defects (“hole in the heart”) and tetralogy of Fallot.
Hypertrophic cardiomyopathy, a heart muscle disease, is found in around 20 percent of patients with Noonan syndrome. This may be present at birth or develop later.
Many individuals with Noonan syndrome have short stature. It is common for height and weight to be below the third percentile on a typical growth chart.
Puberty is often delayed in individuals with Noonan syndrome.
Some individuals are found to have bleeding disorders, mainly problems with the way their blood clots. Mild symptoms may include easy bruising or heavy menstrual cycles in women. Identification is important, as issues with clotting should be recognized before any surgical procedure.
Learning and Development
Delay in reaching early developmental milestones is common for individuals with Noonan syndrome. Feeding difficulties are also common during infancy.
Around 25 percent of individuals have learning disabilities, and some require a special education classroom setting. The average IQ tends to be lower than other family members who do not have Noonan syndrome.
Individuals with Noonan syndrome have similar characteristic facial features that tend to change over time. The facial features can be more subtle and may be hardest to recognize in an adult with Noonan syndrome. Although they share many facial features, individuals with Noonan syndrome also resemble their own family members.
Patients with Noonan syndrome may have a broad or webbed neck.
Differences in structure of the breast bone, located in the center of the chest, are often seen in patients with Noonan syndrome.
Most individuals with Noonan syndrome have some type of eye and/or vision problem. A much smaller percentage may have some degree of hearing loss.
Around 10 percent of individuals have a kidney anomaly. These are typically mild and have little clinical significance. Having a structural kidney problem may make urinary tract infections more likely.