This set of guidelines is designed to assist the pediatrician in caring for the child in whom the diagnosis of Turner syndrome has been confirmed by karyotype. Although the pediatrician's first contact with the child is usually during infancy, occasionally the pregnant woman who has been given the prenatal diagnosis of Turner syndrome will be referred for advice. Therefore, these guidelines offer advice for this situation as well.

Turner syndrome, as used here, refers to a condition in which there is short stature and ovarian dysgenesis in females because of the absence of a normal second sex chromosome. Nonchrornosomal gonadal dysgenesis is excluded. The birth prevalence of Turner syndrome has been estimated to be from 1:2000 to 1:5000 female live births. About 1% to 2% of all conceptuses have a 45,X chromosome constitution. Of these, the majority (99%) spontaneously abort, usually during the first trimester of pregnancy. With the more frequent use of ultrasound, it is recognized that some pregnancies with a fetal 45,X chromosome constitution progressing into the second trimester are associated with nuchal cysts, severe lymphedema, or hydrops fetalis. These pregnancies are associated with a high frequency of fetal death.

PHENOTYPE

Pediatricians are most familiar with the clinical findings that prompt the diagnosis in children, namely, short stature and the classic Turner syndrome features such as lymphederna, webbed neck, low posterior hair line, and cubitus valgus. A wide range of clinical abnormalities may be found (Table 1). Turner syndrome, however, is not always accompanied by distinctive features and most often is not diagnosed in infancy.

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