What is Turner Syndrome?
Table of Contents
Turner syndrome is a sporadic chromosomal disorder that is characterized by a missing or partially deleted X chromosome. This results in a 45, XO female with characteristic developmental disorders affecting sexual maturity i.e., affected females do not undergo normal changes seen in a female during puberty such as menstruation, breast development, axillary, and pubic hair growth, etc. In addition, Turner syndrome also affects the entire body of the patient including the cardiovascular, renal, skeletal, endocrine, sensory, and neurological systems. Statistically, the risk of having a newborn with Turner syndrome is one in every 2000 live female births.
Girl With Turner Syndrome. Image courtesy of Johannes Nielsen
What Causes Turner Syndrome?
Gender can be distinguished genetically by the presence or absence of the Y chromosome. Males have a set of XY chromosomes, while females have XX chromosomes. XX or XY chromosome is what distinguishes males from females during embryogenesis. However, in some rare genetic conditions, there may be a chromosomal disorder in these sex-determining chromosomes such as Turner Syndrome, in which there is a missing X chromosome, that results in a classic constellation of symptoms. Turner syndrome is a sporadic disorder in a majority of cases; therefore it usually cannot be transmitted from one affected parent to a child.
Symptoms and Signs
Women with Turner syndrome present with some characteristic physical features such as short height, swollen feet, and hands, wide chest, the low position of ears, a low-set hairline, obesity, webbing of neck, etc. Turner syndrome, being a multi-systemic disease can have a wide range of symptoms spanning several organs.
Reproductive System: All women born with turner syndrome are invariably infertile. Moreover, the development of secondary sexual characteristics during puberty fails to occur in patients with Turner syndrome. However, both infertility and amenorrhea can be treated pharmacologically with hormone replacement therapy and IVF. With advancements in the field of medicine, there have been increasing documented cases of women born with Turner syndrome conceiving a healthy child.
Cardiovascular System: Some cases of turner syndrome present with congenital heart diseases such as a bicuspid aortic valve, coarctation of the aorta, aortic valve stenosis, aortic regurgitation, aortic dissection. The involvement of the cardiovascular system is seen in up to 45% of patients and is a major cause of early death in Turner syndrome.
Skeletal System: Hormonal deficiency is responsible for the skeletal malformations seen in patients with Turner syndrome. Patients with Turner syndrome are almost always short with an average height of 140cm. Another classic skeletal deformity found in Turner syndrome is an unusually short fourth finger and fourth toe. Estrogen is deficient in all patients with Turner syndrome, and as estrogen plays a major role in bone mineralization, many patients also suffer from osteoporosis, which can result in pathological bone fractures.
Renal System: Approximately 30-40% of Turner syndrome cases have a malformed kidney that can either present as a unilateral horseshoe-shaped kidney, abnormal renal collecting ducts, or decreased renal blood flow. In spite of these anomalies, the renal system functions normally in most cases of Turner syndrome, with a few patients presenting with hypertension associated with renal dysfunction.
Endocrine System: Patients with Turner syndrome are affected by either diabetes or hypothyroidism in up to one-third of cases. However, these can be managed pharmacologically with levothyroxine and insulin therapy.
Neurological System: Women with Turner syndrome have normal intellectual and cognitive function, but some may present with problems in processing information, poor mathematical problem-solving skills, and spatial issues.
Diagnosis Of Turner Syndrome
Turner Syndrome
In developed countries, prenatal screening is commonly done, and therefore chromosomal disorders such as Turner syndrome are usually diagnosed prior to the birth of the fetus. An ultrasound examination during intra-uterine life can diagnose Turner syndrome by identification of the multi-systemic defects associated with Turner syndrome such as aortic disorders, horseshoe-shaped kidneys, ascites, etc. Maternal serum screening can also identify patients with a high risk of Turner syndrome. Prenatal confirmative diagnosis can only be done via karyotyping of the fetal chromosome. Samples for fetal karyotyping can be obtained by amniocentesis during pregnancy. Postnatal diagnosis of Turner syndrome is often obvious just by the characteristic physical features and cardiovascular defects in a newborn baby. The confirmative test of choice for postnatal diagnosis of Turner syndrome is also karyotyping.
Treatment
Turner syndrome is not a curable condition. Its systemic range of symptoms and defects can however be managed via an individualized approach based on the defect present. For instance, hormonal therapy for estrogen deficiency, growth hormone replacement therapy for short stature, anti-hypertensive drugs for hypertension, levothyroxine for hypothyroidism, insulin therapy for diabetes, and surgical repair for aortic disorders are all targeted treatments for patients with Turner syndrome.
Outlook Of Turner Syndrome
Due to a normal cognitive function, most patients with Turner syndrome can potentially have a normal social life but as many women with Turner syndrome suffer from psychological issues, a normal social life may be difficult. Generally, women with Turner syndrome have a lower life expectancy, and this higher mortality rate is associated with Turner syndrome is mostly attributed to the associated cardiovascular disorders.
References
https://ghr.nlm.nih.gov/condition/turner-syndrome
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