What is Patau Syndrome or Trisomy 13

What is trisomy 13 like?

La trisomy 13, Also known as Patau syndrome, is a serious congenital (that is, present from birth) condition characterized by the presence of three copies of chromosome 13.

Chromosome 13

El chromosome 13 It is a type of autosomal chromosome and represents 3,5-4% of the total DNA, present in all human cells. Although researchers have studied it for a long time, they have not yet been able to establish the exact number of genes it contains: the proportion varies between 300 and 700 genetic elements.

In people with trisomy 13, the extra chromosome 13 can be complete (thus completely identical to the normal two) or partial (meaning a part is missing). When complete, it is called total trisomy 13; when it is partial, we talk about partial trisomy 13.

In most Patau syndrome carriers, all cells in the body have three copies of chromosome 13; however, it can rarely happen that trisomy is limited to a certain number of cells. In this second case, geneticists also speak of genetic mosaicism.

How does Patau Syndrome appear?

Usually at the time of conception, the egg (female) and sperm (male) contain 23 chromosomes each. The union of these two elements leads to the formation of the fertilized ovum (the future embryo), which contains 46 chromosomes in total. A trisomy like Patau syndrome usually arises because either the egg or the sperm has an extra chromosome.

El fertilized egg and the future embryo will have cells containing 47 chromosomes and no 46.

Factors riesgo

La advanced age of the mother is a possible risk factor for Patau syndrome. This also applies to the other more common forms of trisomy, such as Down syndrome and Edwards syndrome.

Symptoms and complications

The symptomatological picture depends to a great extent on the severity and the chromosomal alteration. Usually an affected baby has various external and internal physical anomalies, including:

• Small head (microcephaly).
• Holoprosencephaly. It is that particular pathological condition in which the brain is not divided into two hemispheres, as it normally should be. This causes neurological problems (mental retardation) and facial defects of varying severity.
• Espina bifida open. It is the most serious form of spina bifida, which also affects the spinal cord. In people with this condition, the meninges and spinal cord protrude (known as a hernia) from their vertebral housing, forming a protruding sac at the level of the back. Although it is protected by a layer of skin, this bag is exposed to external aggressions and is continually at risk of serious and, in some cases, even fatal infections.
• Wide nose.
• Low and unusual shaped ears; deafness and recurrent ear infections.
• Eye defects of various kinds. Trisomy 13 carriers usually have very small eyes (microphthalmia) and very close to each other (hypotelorism). In severe cases, they have only one eye (anophthalmia) and / or suffer ocular coloboma. The ocular coloboma is a malformation of the eye that can affect the lens, iris, choroid, retina and / or eyelid. Some patients have a complete lack of a retina. Obviously, in the presence of one or more of these conditions, visual abilities are affected.
• Harelip I cleft palate. The first condition consists of a break in the upper lip, while the second condition is a break in the palate.
• Aplasia of the skin (or aplasia skin). It is the medical term for the lack of skin in certain areas of the scalp. Those who carry it are prone to recurrent infections and ulcers. In addition, the skin has a protective function against microorganisms (bacteria, viruses, etc.).
• Polydactyly (o hyperdactyly) Y camptodactyly. The first term refers to having more than five fingers and / or toes. The second term indicates a malformation of both hands, characterized by permanent flexion of the interphalangeal joints.
• In men, cryptorchidism (undescended testicle) and malformations of the scrotum and genitalia (micropenis); in females, bicornuate uterus e clitoral hypertrophy.
• Breathing difficulties and heart defects. Heart defects and abnormalities include so-called interatrial and interventricular defects, patent ductus arteriosus, valvular heart disease (particularly affecting the aortic and pulmonary valves), and dextrocardia (heart shifted to the right, rather than to the right). the left).
• Kidneys with cysts. Its appearance is very reminiscent of the kidneys of people with polycystic kidney disease.
• Gastrointestinal abnormalities.

After one month of life

If the newborn reaches one month of life, he will develop more ailments, including:

• Difficulty eating properly.
• Constipation.
• Gastroesophageal reflux.
• Slow growth rate.
• Scoliosis.
• Tendency to irritability.
• Sensitivity to sunlight (photophobia).
• Reduced muscle tone
• Hypertension.
• Sinusitis and infections of the urinary tract, eyes and ears.

Diagnosis

Doctors can diagnose Patau syndrome even before the baby is born. The tests for the identification of the disease in the prenatal phase are: fetal ultrasound, amniocentesis (transabdominal collection of a small amount of amniotic fluid, it is done at 16 or 18 weeks) and CVS (it is done at 10 or 12 weeks) . It is usually done between week 16 and 18.

If for various reasons it is not possible to carry out the aforementioned controls, the diagnosis of trisomy 13 occurs at birth, through a precise physical examination and chromosomal analysis of a blood sample.

Transmission

Patau syndrome is a incurable illnessSince there is no treatment that can restore normal chromosome composition, neither during prenatal life nor after birth.

However, if the baby survives, symptomatic treatment will be done. What is affected will be addressed.

Forecast

The life expectancy of a person with Patau syndrome is very limited. An Anglo-Saxon study reports that:

• • The median survival rate is 2,5 days.
  • About 50% of affected babies live just over a week.
  • 5-10% of subjects with trisomy 13 live for just over a year.