Turner syndrome

Turner syndrome (TS), commonly known as 45,X, or 45,X0, is a chromosomal disorder in which cells of females have only one X chromosome instead of two, or are partially missing an X chromosome leading to the complete or partial deletion of the pseudoautosomal regions in the affected X chromosome. Humans typically have two sex chromosomes, XX for females or XY for males. The chromosomal abnormality is often present in just some cells, in which case it is known as Turner syndrome with mosaicism. 45,X0 with mosaicism can occur in males or females, but Turner syndrome without mosaicism only occurs in females. Signs and symptoms vary among those affected but often include a short neck that is webbed or wide, arched palate, low-set ears, low hairline at the nape of the neck, short stature, and lymphedema of the hands and feet. Those affected do not normally develop menstrual periods or mammary glands without hormone treatment and are unable to reproduce without assistive reproductive technology. Small chin (micrognathia), loose folds of skin on the neck, slanted eyelids and prominent ears are found in Turner syndrome, though not all will show it. Heart defects, Type II diabetes, and hypothyroidism occur in the disorder more frequently than average. Most people with Turner syndrome have normal intelligence; however, some have problems with spatial visualization that can hinder learning mathematics. Ptosis and conductive hearing loss also occur more often than average.

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