Bonnevie-Ullrich syndrome

Alternative names

Turner syndrome; Gonadal dysgenesis; Monosomy X

Definition

Turner syndrome is a birth defect caused by the absence of an X chromosome in some or all cells of a female, which inhibits sexual development and usually causes infertility.

Causes, incidence, and risk factors

A person's sex is determined by two chromosomes, the X and the Y. Usually, men have an X and a Y, while women have two X's. In Turner syndrome, a baby girl develops with only one X chromosome. The incidence is 1 out of 3,000 live births.

Turner syndrome usually occurs sporadically, which means that the mutation occurs in fetal development and is not inherited from either parent. In rare cases, a parent silently carries rearranged chromosomes that can result in Turner syndrome in a daughter; this is the only situation in which Turner syndrome is inherited.

Girls with Turner syndrome usually have short stature, webbing of the skin of the neck, absent or retarded development of secondary sexual characteristics at puberty, absence of menstruation, coarctation (narrowing) of the aorta, bicuspid aortic valve, and abnormalities of the eyes and bones. The condition is either diagnosed at birth because of the associated anomalies, or at puberty when there is absent or delayed menses and delayed development of normal secondary sexual characteristics.

IQ is generally normal although some children have learning difficulties. More than half of all patients with Turner syndrome are mosaics, which means that the mutation occurs in some but not all of the cells of their body. This means that it can vary in severity since the fewer cells affected, the more mild the disease will be.

Symptoms

• Short stature
  
• Webbed neck
  
• Abnormal eye features (drooping eyelids)
  
• Abnormal bone development, such as a "shield-shaped", broad, flat chest
  
• Absent or retarded development of secondary sexual characteristics that normally appear at puberty, including sparse pubic hair and small breasts
  
• Infertility
  
• Dry eyes
  
• Absent menstruation
  
• Absence of normal moisture in vagina; painful intercourse
  

Signs and tests
During a physical examination, the doctor will look for signs of underdeveloped breasts and genitalia, webbed neck, short stature, low hairline in back, simian crease (a single crease in the palm), and abnormal development of the chest. Infants with Turner syndrome often have swelling of the hands and feet, probably reflecting changes in drainage in the lymphatic system.