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Patient Story

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A 6-year-old girl is brought to the pediatrician because of swelling in her lower legs that was noted by her mother over the past few weeks. The child has otherwise been well. Review of the growth parameters showed the girl to be at less than the 5th percentile for height. The girl exhibited edema of the lower extremities (right > left), low set ears, ptosis, and mild micrognathia (Figures 222-1 and 222-2). The pediatrician suspected Turner syndrome and referred the child to a pediatric endocrinologist, who confirmed the diagnosis with a karyotype (45, XO pattern). The child and family received counseling and education, and the girl was treated with growth hormones and has done well. Screening tests for renal and cardiac abnormalities were normal.

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FIGURE 222-1

Lymphedema in the lower extremities, which is especially prominent on the right, in a 6-year-old girl with Turner syndrome. This was the presenting feature of this syndrome in this girl. (Used with permission from Camille Sabella, MD.)

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FIGURE 222-2

Low set ears, low hairline, mild ptosis, and small lower jaw in the same 6-year-old girl in Figure 222-1. (Used with permission from Camille Sabella, MD.)

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Introduction

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Turner syndrome is an absence of one of the X chromosome (partial or complete) with a resultant female phenotype of short stature, lack of normal sexual maturation, and diverse somatic findings.

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Synonyms

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Gonadal dysgenesis, Haploinsufficiency of the X chromosome (45, XO karyotype), Bonnevie-Ullrich syndrome, and monosomy X.

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Epidemiology

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  • Turner syndrome is the most common sex-linked chromosomal abnormality.

  • Turner syndrome is a common cause of first-trimester spontaneous abortions, accounting for approximately 20 percent of the spontaneous abortions caused by chromosomal defects.

  • Incidence is 1/2,500 to 1/5,000 live births; only 5 to 10 percent of affected fetuses survive to birth.1

  • There are roughly 50,000 to 75,000 cases total in the US

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Etiology and Pathophysiology

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  • Turner syndrome is a chromosomal abnormality caused by complete or partial absence of the second sex chromosome in a woman (most common karyotype is 45, XO) or mosaicism (e.g., karyotype 46, XX/45, XO or 46, XY/45, XO).

  • Not related to maternal age.

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Diagnosis

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The diagnosis of Turner syndrome is suspected on clinical features and confirmed by chromosomal analysis. Any girl with pathological short stature should have a karyotype performed to rule out Turner syndrome.2,3

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Clinical Features
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  • Can be identified at birth by the presence of lymphedema and excessive skin folds in the neck—Present in 30 percent of cases (Figures 222-3 and 222-4).4...

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