Noonan syndrome

Alternative names:

Turner-like syndrome

Definition:

A grouping of specific abnormalities affecting both males and females, both sporadic in appearance but also reflecting a hereditary component (thought to be autosomal dominant).

Causes, incidence, and risk factors:

In some families, Noonan syndrome may have a male-to-male transmission pattern. The symptoms vary. Frequently seen abnormalities include webbing of the neck, changes in the sternum (usually a sunken chest called pectus excavatum), facial abnormalities, and congenital heart disease (usually pulmonic stenosis).

Facial abnormalities may include low-set or abnormally shaped ears, sagging eyelids (ptosis), wide-set eyes (hypertelorism), epicanthal folds, and a small jaw (micrognathia). Mild mental retardation may be present. Hearing loss varies. Puberty is usually delayed, and males may have undescended testicles and a small penis. Adult height is usually decreased.