Turner Syndrome Diagnosis

Diagnosis of Turner Syndrome in terms of the karyotype:

Turner Syndrome is often suspected in pregnancy if an ultrasound test identifies problems like heart defect, kidney abnormality, cystic hygroma, ascites. The result of this test is further confirmed by prenatal testing – chorionic villous sampling or amniocentesis – to obtain cells from the unborn baby for chromosomal analysis. Of the prenatal tests, amniocentesis is the most prominent. In this procedure, a small amount of amniotic fluid, which contains fetal tissues, is extracted from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for genetic abnormalities. Nevertheless, the predictive value of amniocentesis in diagnosing Turner syndrome varies from 21-67% and there is a probability of 1 in every 2500 girls being born with this syndrome.

Girls with Turner Syndrome are diagnosed either at birth or at the age of puberty, depending on the severity of the condition. Girls with severe Turner Syndrome may show signs/symptoms at an early age (infancy or early childhood). On the other hand, however, girls with minor Turner Syndrome may show signs later in life (mostly during the age when a girl normally undergoes puberty). Some of the visible features of Turner Syndrome are short height, webbed neck, broad chest, low hairline, low-set ears, ear infections, and small fingernails.

In any case, once the signs of Turner Syndrome are demonstrated, a doctor will conduct a special blood test called the Karyotype. This test analyzes the chromosomal composition, or counts the number of chromosomes, and can identify any chromosomes that are abnormally shaped or have missing pieces. (The karyotype of X monosomy, which is the most common cause of Turner Syndrome, is termed “45X” — meaning that an individual has 44 autosomes and a single X chromosome.) If the Karyotype blood test reveals that a girl indeed has Turner Syndrome, her doctor may order additional tests to check for problems with the kidneys, heart, hearing, and other problems associated with this condition.

The diagnosis of Turner Syndrome caused by X chromosome defects may require specialized, molecular cytogenetic studies to identify small deletions or inversions of X chromosome material. The genetic diagnosis of mosaic Turner Syndrome may require the examination of many blood cells, and/or the examination of other cell types such as skin cells. The genotype of mosaic Turner syndrome is usually specified as 45X (10)/46XX (90) to indicate, for example, that 10 percent of cells examined were found to have X monosomy.