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, 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 an affected 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:
Are males with Noonan syndrome capable of fathering children (fertile)?
Male pubertal development and subsequent fertility may be normal, delayed, or inadequate. Sixty to eighty percent of males with Noonan syndrome have undescended testicles (cryptorchidism) which can lead to infertility (inability to father a child) later in life.
Last updated: 3/2/2010
How is Noonan syndrome inherited?
Noonan syndrome is inherited in an autosomal dominant manner. This means that having one changed (mutated) copy of the responsible gene in each cell is enough to cause the condition. Each child of a person with Noonan syndrome has a 50% (1 in 2) chance to inherit the condition.
In some cases, the condition is inherited from an affected parent. Because the features of the condition can vary and may be very subtle, many affected adults are diagnosed only after the birth of a more obviously affected infant. In other cases, the condition is caused by a new mutation occurring for the first time in the affected person.
Last updated: 6/2/2015
Are the children of an individual with Noonan syndrome at risk to inherit the condition?
Each child of an individual with Noonan syndrome has a 50% chance of inheriting the mutation.
Last updated: 3/2/2010
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