What is Noonan Syndrome?

Noonan Syndrome is a genetic disorder causing short stature, characteristic facial features, heart defects, and other abnormalities. It is sometimes called "male Turner syndrome" due to similarities, but it affects both sexes and has different genetics.

Key Features:

• Facial Features: Widely spaced eyes (hypertelorism), low-set ears, webbed neck, droopy eyelids
• Short Stature (50-70%): Growth hormone deficiency common
• Cardiac Defects (50-80%): Pulmonary stenosis most common, hypertrophic cardiomyopathy
• Cryptorchidism (Undescended Testes) in Males (60-80%)
• Bleeding/Bruising Tendency: Clotting abnormalities
• Developmental Delays (Mild): Learning disabilities
• Chest Deformity: Pectus carinatum/excavatum

Endocrine Issues:

• Growth Hormone Deficiency (GHD): Common cause of short stature
• Delayed Puberty
• Cryptorchidism/Hypogonadism (Males)
• Thyroid Disorders

Genetics & Diagnosis:

• PTPN11 Gene (Most Common): ~50% of cases; also RAS pathway genes
• Autosomal Dominant: 50% hereditary, 50% de novo
• Affects Both Sexes Equally
• Diagnosis: Clinical features + genetic testing

Treatment:

• Growth Hormone Therapy: FDA-approved for Noonan syndrome; improves height
• Cardiac Monitoring/Treatment: For congenital heart defects
• Orchiopexy: Surgery for undescended testes
• Testosterone Replacement: If hypogonadism
• Developmental/Educational Support
• Bleeding Precautions: Avoid NSAIDs; clotting studies before surgery

Prognosis:

• Variable depending on severity of cardiac defects
• Most have normal intelligence and life expectancy
• Increased cancer risk (leukemia, neuroblastoma) in childhood