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Chromosomal disorder with a specific aspect (pterygium
colli short neck and gonadal insufficiency).
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Turner-Varney Syndrome; 45X Syndrome; Bonnevie-Ulrich
Syndrome; Monosomy X; XO Syndrome; Turner Syndrome.
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X-linked chromosomal disorder resulting from one functional
X chromosome. 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.
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1:2500 live births in the female gender.
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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.
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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.
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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-loosing 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 patients 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),
gonadal dysgenesis (95% of patients), ...