Turner syndrome is a disorder that occurs when there is a complete or partial monosomy of the X chromosome. Turner syndrome is associated with one of the following 3 types of karyotypic abnormalities·
45,X karyotype ( in which no Barr bodies are seen in the buccal smear)· mosaics (45, X cell plus one or more karyotypically normal or abnormal cell types)·
Structural abnormalities of the X chromosomes which result in partial monosomy of the X chromosome. E.g. deletion of one of the arms of the X chromosome.
This karyotypic heterogeneity associated with Turner’s syndrome is responsible for significant variations in phenotype. E.g. 45, XO causes a severe phenotype whereas mosaics may have a normal appearance with only primary amenorrhea.
Turner syndrome is characterized by female hypogonadism and its secondary effects.
Replacement of the ovaries by fibrous streaks.
Decreased estrogen production & increased pituitary gonadotropins from loss offeedback inhibition.
Infantile genitalia and poor breast development and little pubic hair.
Short stature (rarely exceeding 150cm in height), webbed neck, shield-like chestwith widely spaced nipples, and wide carrying angles of the arms.
Lymphedema of the extremities and neck.
Congenital heart disease (especially preductalcoarctation of the aorta and bicuspidaortic valve).