X-linked chromosomal disorder with karyotype containing one X chromosome and complete or partial absence of the second sex chromosome, associated with one or more typical clinical manifestations: pterygium colli short neck and gonadal insufficiency.
Turner-Varney Syndrome; 45X Syndrome; Bonnevie-Ulrich Syndrome; Monosomy X; XO Syndrome; Turner Syndrome.
First described by Henry Hubert Turner, American endocrinologist in 1938, in a patient with sexual infantilism, webbed neck, cubitus valgus, and short stature. The genetic basis was recognized in 1959 by C. E. Ford et al.
1:2,500 live births in the female gender.
Caused by a defect of one entire chromosome X (50% of patients), mosaicism (20% of patients), or two chromosomes X but one abnormal (30% of patients). Nearly 99% of XO fetuses are aborted. The primary defect is thought to be abnormal development of lymphatic channels in utero, resulting in fetal lymphedema, which prevents normal growth, rotation, and regression of fetal tissues, thus causing the Turner phenotype.
Small stature, short and broad neck, hypoplasia of the cervical vertebrae, pterygium colli, and gonadal dysgenesis are the most frequent and characteristic signs of the disease. Age of onset is variable according to the presentation: infant: lymphedema; childhood: short stature; adolescence: primary or secondary amenorrhea. Risk factors include advanced paternal age (isochromosome X cases) and mother affected with a mosaic or dilational variant of the Turner Syndrome. For certitude, the diagnosis can be confirmed using karyotype studies.
Clinical features can concern all systems and part of the bodies: head (micrognathia, midfacial hypoplasia, deepening of the posterior cranial fossa, widely spaced mandible, large ears, blepharoptosis strabismus, epicanthal folds, highly arched palate, occasional cleft palate, premature tooth eruption), skeleton (thin ribs, short metacarpal and metatarsal bones, drumstick distal phalanges, pes cavus, Madelung deformity, cubitus valgus, deformed tibial condyles, hypoplastic and dislocated patellae, faulty fusion of the epiphyses, scoliosis, osteoporosis), cardiovascular system (coarctation of the aorta, dissecting aortic aneurysm, ventricular septal defect, atrial septal defect, dextrocardia, bicuspid aortic valve, hypoplastic left heart), abdomen (prune belly, telangiectases, hemangiomas, intestinal bleeding, protein-losing enteropathy), genitourinary system (unilateral aplasia or hypoplasia of the kidneys, horseshoe kidneys, malrotation of the kidneys, duplication dysgenesis, and streak gonads), endocrinopathy (hypothyroidism, Hashimoto disease, diabetes mellitus), and skin and dermatoglyphs (puffy hands and feet, pigmented nevi, seborrhea, xerosis, keloid, nail hypoplasia, low hairline, hirsutism). Abnormally placed nipples are also very frequent. Mental retardation, deafness, blindness, anorexia nervosa, amenorrhea, and sterility can occur. This complex polymalformative syndrome benefits of many symptomatic treatments that have greatly improved outcome. Features vary with age of presentation: newborn: lymphedema of the hands and feet, small for age, and excessive skin at nape of the neck; childhood and adolescence: short stature (98% of patients), ...