Noonan syndrome 4

Noonan syndrome is a genetic disorder that causes abnormal development of multiple parts of the body. Features of Noonan syndrome may include a distinctive facial appearance, short stature, a broad or webbed neck, congenital heart defects, bleeding problems, problems with bone structure (skeletal malformations), and developmental delay. Noonan syndrome may be caused by a mutation in any of several genes, and can be classified into subtypes based on the responsible gene. It is typically inherited in an autosomal dominant manner, but many cases are due to a new mutation and are not inherited from either parent. Treatment depends on the symptoms present in each person.

Noonan syndrome belongs to a group of related conditions called the RASopathies. These conditions have some overlapping features and are all caused by genetic changes that disrupt the body's RAS pathway, affecting growth and development. Other conditions in this group include:

• neurofibromatosis type 1
• LEOPARD syndrome, also called Noonan syndrome with multiple lentigines
• Costello syndrome
• cardiofaciocutaneous syndrome
• Legius syndrome
• capillary malformation–arteriovenous malformation syndrome