Turner Syndrome
Incidence
1 in 2500 female births with 10-fold higher incidence at conception.Minimal recurrence risk for parents except in rare cases of translocation; mosaic females who are fertile have an increased risk for chromosomal anomalies in their offspring.
Clinical Characteristics
Malformation syndrome in females with neonatal pedal edema, webbed neck, heart anomalies and later short stature with immature sexual development. Chromosome studies will define the diagnosis of Turner syndrome, with about 1/3 of patients presenting in the newborn period, 1/3 during childhood, and 1/3 during adolescence because of delayed puberty. A buccal smear to show the absence of a Barr body is not sufficient for diagnosis; older patients diagnosed on this basis should have a karyotype to rule out the presence of a Y chromosome. It is now possible to screen for mixtures of Turner and normal cells (mosaicism) using the technique called fluorescent in situ hybridization (FISH). Several tissue types such as the oral mucosa or urinary sediment can be screened when the peripheral blood chromosome studies suggest mosaicism. Examination of several tissues in patients with Turner syndrome has indicated that mosaicism may be as frequent as 80%. Complications of Turner syndrome include eye, ear, cardiovascular, lymphatic, urinary tract, genital, and autoimmune problems. Mosaic patients will generally have a milder course, except that patients with a Y chromosome-containing cell line face a 25% risk of the development of a gonadoblastoma tumor in their defective ovary. Biochemical abnormalities may be respresented by an increased risk for osteoporosis (softening of the bones) and abnormal blood cholesterol and lipoprotein profiles.Cardiac anomalies such as coarctation of the aorta and bicuspid aortic valve are sufficiently common that an echocardiogram should be considered during infancy. There is increased risk of autoimmune disorders, including hypothyroidism and diabetes mellitus. Obesity can also be a problem.
Precipitants
none
Provocation Tests
none
Diagnostic Procedures
45,X karyotype in the majority with rarer deletions of Xp or Xq; 1/3 of patients are mosaic. Chromosome studies will define the diagnosis of Turner syndrome, with about 1/3 of patients presenting in the newborn period, 1/3 during childhood, and 1/3 during adolescence because of delayed puberty. A buccal smear to show the absence of a Barr body is not sufficient for diagnosis; older patients diagnosed on this basis should have a karyotype to rule out the presence of a Y chromosome. It is now possible to screen for mixtures of Turner and normal cells (mosaicism) using the technique called fluorescent in situ hybridization (FISH). Several tissue types such as the oral mucosa or urinary sediment can be screened when the peripheral blood chromosome studies suggest mosaicism. Examination of several tissues in patients with Turner syndrome has indicated that mosaicism may be as frequent as 80%.