Turner syndrome
Turner syndrome, also known as 45,X or 45,X0, is a chromosomal abnormality characterised by a partial or completely missing second X chromosome,
giving a chromosomal count of 45, instead of the typical count of 46 chromosomes.Dysregulation in meiosis signalling to germ cells during embryogenesis may result in nondisjunction and monosomy X from separation failure of chromosomes in either the parental gamete or during early embryonic divisions.The aetiology of Turner syndrome phenotype can be the result of haploinsufficiency, where a portion of critical genes are rendered inactive during embryogenesis. Normal ovarian development requires these vital regions of the X chromosome that are inactivated. Clinical manifestation include primary amenorrhea, hypergonadotropic hypogonadism, streak gonads, infertility, and failure to develop secondary sex characteristics. Turner syndrome is not diagnosed until a delayed onset of puberty with Müllerian structures found to be in infantile stage. Physical phenotypic characteristics include short stature, dysmorphic features and lymphedema at birth.Comorbidities include heart defects, vision and hearing problems, diabetes, and low thyroid hormone production. Endocrine disruptions
Endocrine disruptors interfere with the endocrine system and hormones. Hormones are critical for the correct events in embryogenesis to occur.Foetal development relies on the proper timing of the delivery of hormones for cellular differentiation and maturation. Disruptions can cause sexual development disorders leading to gonadal dysgenesis. Diagnosis
Management
History
Turner syndrome was first described independently by Otto Ulrich in 1930 and Henry Turner in 1938. 46,XX pure gonadal dysgenesis was first reported in 1960. 46,XY pure gonadal dysgenesis, also known as Swyer syndrome, was first described by Gim Swyer in 1955.
See also
(DoDI) 6130.03, 2018, section 5, 13f and 14m
Ovotestis
46 XX

References


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