Noonan syndrome

Noonan syndrome (Noonan–Turner syndrome, also sometimes referred to as “male Turner syndrome”) is a congenital genetic disorder caused by gene mutations that result in a characteristic set of symptoms, including congenital heart defects, short stature, and distinctive facial features. Noonan syndrome is sometimes referred to as male Turner syndrome (45,X0), although it is a genetically distinct condition. Inheritance is autosomal dominant. Approximately one child in 1,000–2,500 newborns is born with this syndrome.

Both sexes are affected equally. The syndrome was first described in 1962 by pediatric cardiologist Jacqueline Noonan and was recognized as a separate diagnostic entity in 1971.

Diagnosis:
Diagnosis is based on genetic testing, which can also be performed prenatally. Noonan syndrome should be considered in a fetus with polyhydramnios, pleural effusions, edema, and nuchal edema in the presence of a normal karyotype.

Treatment:
The therapeutic approach should focus on early nutritional support in infancy, assessment of cardiovascular function, and possible surgical management of congenital heart defects, as well as evaluation of the child’s growth and motor development. If needed, physiotherapy and speech therapy should be provided. In the early school years, a complete ophthalmological examination as well as hearing assessment should be performed. Due to a tendency toward hemorrhagic complications, coagulation parameters must be evaluated before any surgical procedure. With appropriate specialized care and family counseling, most children with Noonan syndrome can integrate into normal life in adulthood. Characteristic symptoms tend to become less pronounced over time, and most patients do not require special medical care in adulthood. 

• Facial dysmorphism includes hypertelorism (present in about 95% of patients, with increased distance between the eyes), antimongoloid slant of the palpebral fissures, ptosis of the eyelids (drooping eyelids), and low-set, posteriorly rotated ears with a thickened helix (the outer rim of the ear forming a rolled or folded edge).
• Typical occurrence of congenital heart malformations in up to 2/3 of patients
• Stenosis – narrowing of heart valves (especially the pulmonary valve)
• Septal defects – defects of the cardiac septa (atrial septal defect or ventricular septal defect)
• Functional heart murmur
• Gastrointestinal symptoms (vomiting, reduced appetite, swallowing disorder)
• Weight loss up to development of cachexia
• Cryptorchidism in boys – undescended testes
• Frequent lymphedema
• Coordination disorders, clumsiness
• Reduced intellect
• Memory impairment
• Delayed speech development
• Short stature
• Short neck
• Low posterior hairline
• Scoliosis
• Pectus carinatum (pigeon chest) or pectus excavatum (sunken chest)
• Macrocephaly – large head
• Sometimes also myalgia – muscle pain
• Thrombocytopenia – low platelet count
• Often associated with von Willebrand disease
• Increased risk of bleeding