Genetic basis and cytogenetic diagnostics
Turner syndrome is a unique genetic anomaly. To date, it is the only known viable human sex chromosome monosomy.
The karyotype of such patients is designated as 45, X0 (according to the classification, this is monosomy X). In the general population, this pathology occurs with a frequency of 1:3000.
To confirm the diagnosis, a cytogenetic study is performed, specifically a sex chromatin test. The material for the study is buccal epithelium — cells of the oral mucosa. Upon microscopy, these cell nuclei lack the Barr body, which should normally be detected in females. Due to this diagnostic sign, the status of such patients is defined as chromatin-negative.
Clinical presentation and appearance
Despite the absence of one X chromosome, patients with Turner syndrome are exclusively female. However, their appearance (phenotype) has a number of specific, easily recognizable features:
- Short stature: patients exhibit pronounced growth retardation.
- Disproportionate body structure: it is visually noticeable that the length of the upper half of the torso significantly exceeds the lower half.
- Neck anomalies: the neck is shortened, with wide cutaneous pterygoid folds (webbed neck). This anatomical feature gives patients a characteristic appearance resembling a sphinx's head.
- Premature aging: there is a general predisposition of the organism to early aging.
Reproductive system pathology
The primary anatomical defect in Syndromum Turner lies in gonadal agenesis or dysgenesis — their normal development is completely disrupted. If a laparotomy is performed, the macroscopic picture shows that only an undifferentiated whitish streak gonad is located in place of the gonads.
This defect leads to severe consequences for sexual development:
- Internal genital organs remain underdeveloped.
- There is a general delay in sexual development.
- Secondary sexual characteristics are poorly developed or entirely absent.
- Patients lack a menstrual cycle (amenorrhea).
- In the vast majority of cases, permanent infertility is diagnosed.
Briefly: answers to topical questions
What congenital cardiovascular malformations often accompany Turner syndrome?
Turner syndrome is accompanied by various congenital heart and vascular defects. The provided materials do not specify exact cardiological nosologies, but it is noted that cardiovascular malformations are detected in a significant portion of patients (occurring in 25% of patients alongside renal pathology).
What urinary system anomalies are characteristic of patients with Turner syndrome?
Patients with Turner syndrome are characterized by congenital renal defects, which are detected in 25% of patients. Specifically, the following pathology is associated with this chromosomal disease:
- Horseshoe kidney — a fusion anomaly resulting from impaired migration of both kidneys with fusion along the midline.
What hormone replacement therapy is used in the treatment of Turner syndrome?
For Turner syndrome, the sources indicate hormone therapy with combined estrogen-progestin medications. Additionally, growth hormone (somatotropin) therapy can be effective for syndromic growth retardation, including in Turner syndrome, though high doses are required.
For memorizing appearance and genetics: "Sphinx without a Barr body." Webbed neck folds create the sphinx appearance, while monosomy 45, X0 causes the absence of the Barr body in the epithelium.
Class and exam questions
What karyotype is characteristic of Turner syndrome?
The patients' karyotype is 45, X0, which means the presence of only one sex X chromosome (monosomy).
What does the sex chromatin test show in this pathology?
The nuclei of buccal epithelial cells (oral mucosa) lack the Barr body. Patients are chromatin-negative.
What is the macroscopic picture of the gonads during laparotomy?
Due to agenesis or dysgenesis, an undifferentiated whitish streak gonad is found in place of normal gonads.
Why do patients with this syndrome have an appearance resembling a sphinx's head?
This appearance is formed due to a combination of a very short neck and the presence of wide webbed skin folds on it.
What else to study on this topic
- Mechanisms of X chromosome monosomy formation
- Pathogenesis of growth retardation and disproportionate body structure development
- Histological structure of the undifferentiated streak gonad
- Causes of the predisposition to premature aging in karyotype 45, X0
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