What is Turner syndrome?

What is Turner Syndrome?

Turner syndrome is a genetic condition affecting females caused by complete or partial loss of one X chromosome, occurring in approximately 1 in 2,500 liveborn girls, and is characterized by short stature, ovarian failure, and significantly increased cardiovascular mortality, particularly from aortic dissection. 1, 2

Genetic Basis

• The condition results from either complete monosomy X (45,X) in 40-50% of cases or various mosaic karyotypes including isochromosome X, ring X, or Y chromosome mosaicism 2, 3
• The paternal X chromosome is absent in three-quarters of patients, though this finding has no clinical utility in routine care 2
• Approximately 99% of Turner syndrome conceptions result in pregnancy loss, making liveborn cases relatively rare survivors 2

Cardinal Clinical Features

Growth and Development

• Short stature is one of the two most prevalent findings and occurs in nearly all untreated patients 1
• Additional physical features include lymphedema, webbed neck, and characteristic facial features 1

Reproductive System

• Ovarian dysgenesis and premature ovarian failure are universal features, with hypergonadotropic hypogonadism and infertility being the norm 1, 4
• Only 30% of girls experience some pubertal development, 10-20% reach menarche, and merely 2-8% achieve spontaneous pregnancy 5
• Accelerated germ cell apoptosis leads to premature ovarian insufficiency 5

Cardiovascular Complications (The Most Critical Concern)

Structural Abnormalities

• Approximately 50% of patients have cardiovascular defects, including bicuspid aortic valve (15-30%), aortic coarctation (7-18%), and ascending aortic dilation (33%) 1
• These structural abnormalities are the primary drivers of increased mortality in this population 1, 6

Aortic Dissection Risk

• Aortic dissection is the most feared complication and can occur at very young ages, representing a major cause of premature death 1, 6
• Women with Turner syndrome have dramatically increased cardiovascular mortality from both structural and ischemic heart disease compared to the general population 1

Associated Medical Conditions

• Endocrine disorders including type 1 and type 2 diabetes mellitus are common 4, 3
• Autoimmune disorders occur at increased frequency 4, 3
• Osteoporosis develops due to estrogen deficiency 4
• Neurocognitive deficits may be present 3
• Auditory and visual system abnormalities require monitoring 5

Diagnostic Considerations

• The average age at diagnosis is approximately 15 years, representing substantial diagnostic delay despite often conspicuous phenotype 4
• Prenatal ultrasound findings may include cystic hygroma and hydrops 2
• Recurrence risk for phenotypically normal parents is low 2

Critical Management Imperatives

Cardiovascular Surveillance

• All women with Turner syndrome must undergo baseline cardiovascular imaging to evaluate for bicuspid aortic valve, coarctation, and ascending aortic enlargement 1, 7
• Cardiac MRI is recommended at diagnosis to evaluate congenital cardiovascular abnormalities and measure aortic diameters 1

Pregnancy Considerations

• Pregnancy carries substantially higher risk of aortic dissection, especially with pre-existing cardiovascular abnormalities 1, 7
• Thorough cardiovascular evaluation is mandatory before attempting pregnancy 1, 7

Multisystem Nature

Turner syndrome necessitates lifelong multidisciplinary care involving endocrinology, cardiology, reproductive medicine, and other specialties due to involvement of multiple organ systems through all life stages 4, 3