Monosomies are a type of chromosomal disorder in which some or all of the body’s cells contain a single pair of a chromosome that should be duplicated. One of the few human monosomies compatible with life is Turner syndrome, in which the defect occurs in the female sex chromosome.

In this article we will describe the symptoms and causes of the main types of Turner syndrome , as well as the treatment options commonly used in these cases.

What is Turner syndrome?

Turner syndrome is a genetic disorder that occurs as a result of random alterations in the X chromosome . It does not usually affect intelligence, so people with this disorder usually have a normal IQ.

It is associated with the presence of a single X chromosome in cases where there should be two, so Turner syndrome is diagnosed almost exclusively in girls, although there is a subtype that appears in boys. It occurs in approximately 1 in 2,000 female births.

This disorder affects physical development, especially because of its inhibitory effects on sexual maturation : only 10% of girls with Turner syndrome show some signs of having reached puberty, while only 1% have babies without medical intervention.

Main symptoms and signs

Girls and women with this disorder have two characteristic features that are at the core of the diagnosis: their height is shorter than normal and their ovaries are not fully developed , so they have amenorrhea or menstrual irregularity and cannot become pregnant.

Because the basic signs of Turner syndrome are related to biological maturation and sexual development, it is not possible to definitively identify the presence of this disorder at least until puberty, when these signs begin to manifest themselves clearly.

Other common symptoms of Turner syndrome vary from case to case. Some of the more common symptoms include the following:

  • Morphological abnormalities in the face, eyes, ears, neck, extremities and chest
  • Swelling from fluid accumulation (lymphedema), often in the hands, feet, and neck (thixag__4)

  • Visual and hearing problems
  • Delays in growth
  • Puberty does not complete spontaneously
  • Infertility
  • Short stature
  • Heart, kidney and digestive disorders
  • Deficits in social interaction
  • Learning difficulties, especially in mathematical and spatial tasks
  • Hypothyroidism
  • Scoliosis (abnormal curvature of the spine)
  • Increased risk of diabetes and stroke
  • Hyperactivity and attention deficit

Types and causes of this disease

Turner syndrome is due to the absence of one of the two X sex chromosomes in persons of the biological female sex, although sometimes it also appears in males who have an incomplete Y chromosome and therefore develop as females.

Three types of Turner syndrome have been described depending on the specific genetic causes of the symptoms. These chromosomal alterations occur at fertilisation or during the early stage of intrauterine development.

1. By monosomy

In the classic variant of this syndrome, the second X chromosome is totally absent from all body cells due to defects in the egg or sperm . Successive divisions of the zygote reproduce this base abnormality.

2. With mosaicism

In Turner syndrome of the mosaic type, it is possible to find an extra X chromosome in most cells, but it is either not complete or has some defect.

This subtype of the syndrome develops as a consequence of altered cell division from a certain point in early embryonic development: cells arising from the defective lineage do not have the second X chromosome, while the rest do.

3. With incomplete Y chromosome

In some cases, individuals who are male from a genetic point of view do not develop in a normative way because the Y chromosome is absent or has defects in part of the cells, so they look female and may also have the symptoms we have described. This is a rare variant of Turner syndrome.

Treatment

Although Turner syndrome cannot be “cured” because it consists of a genetic variation, there are different methods that can resolve or at least minimize the main symptoms and signs .

Morphological alterations and other similar associated defects tend to be difficult to modify, although this depends on the specific alteration. Depending on the case, the intervention of specialists such as cardiologists, endocrinologists, otolaryngologists, ophthalmologists, speech therapists or surgeons, among others, may be necessary.

In cases where this disorder is detected early, growth hormone injection therapy promotes the attainment of normal adult height. Sometimes they are combined with low doses of androgens in order to enhance the effects of this treatment.

Hormone replacement therapies are most often applied to girls with Turner syndrome when they reach puberty to enhance their biological maturation (e.g. to promote the onset of menstruation). Treatment is usually started with estrogen and later with progesterone.