Patau Syndrome - Types, Symptoms, Causes and Treatment

Introduction:

Patau syndrome or trisomy 13 is a chromosomal syndrome where there is an extra copy of chromosome 13 in some or all the body cells instead of the usual two copies of the chromosome. This syndrome causes severe physical and intellectual disabilities that affect multiple organs. Most of these babies do not survive more than a year. Trisomy 13 affects the heart, brain, and spinal cord and also causes physical deformities. They are diagnosed mostly during routine prenatal assessments.

Who Discovered Trisomy 13?

Dr. Patau et al. first observed this condition in 1960. They noticed severe cerebral defects, cleft palate, and cleft lip in the neonates.

What Are the Other Names of Patau Syndrome?

• Bartholin Patau syndrome.

• Complete trisomy 13 syndrome.

• Trisomy 13 syndrome.

What Are the Types of Patau Syndrome?

Patau syndrome is classified into three main types. They are:

1. Trisomy 13 - An extra chromosome is seen in all the body cells.

2. Mosaic Trisomy 13 - In the mosaic type, extra genetic material is seen only in some body cells.

3. Partial Trisomy - Here, only a part of the extra chromosome is seen attached to the 13th chromosome.

The presence of extra genetic material is responsible for the condition, and it interferes with the growth and development of the child.

What Is the Incidence of Patau Syndrome?

• It affects 1 in 16000 live births.

• The risk of Patau syndrome increases with maternal age (above the age of 35 years).

• The median life expectancy is seven to ten days. 90 % of the affected patients die during the first year of life.

• Females are more commonly affected than males.

• It has got no racial predilection.

What Is the Cause of Patau Syndrome?

Trisomy 13 is caused due to the presence of an extra copy of the genetic material in the 13th chromosome. The incidence of trisomy 13 increases with maternal age. During conception, when a normal egg and a normal sperm fuse, it results in 46 chromosomes. The mother and father provide 23 chromosomes each. But in the case of trisomy 13, during the fusion of egg and sperm, an abnormal or extra copy of a chromosome is seen in the baby. Sometimes this extra genetic material may be attached to some other chromosomes. This process is known as the translocation of genes.

What Are the Signs and Symptoms of Trisomy 13?

1. They have restricted intrauterine growth and low birth weights.

2. Failure to thrive with low intellectual abilities.

3. Facial deformities such as:

   • Cleft palate and cleft lips.

   • Sloping forehead with a relatively small head (microcephaly).

   • Clenched hands or overlapping of fingers.

   • Malformation of ears that are low set.

   • Preauricular tags (presence of rudimentary ear tissue or cartilage).

   • They are present with only one or both eyes and may be small in size (anophthalmia or microphthalmia).

   • Presence of extra fingers (polydactyly).

4. Cardiac septal defects such as:

   • Ventricular septal defect.

   • Atrial septal defect.

   • Tetralogy of Fallot.

5. Other vital structures, such as the kidney and gastrointestinal tract, are also affected.

6. The skin is missing in the scalp region, and sores are seen on the scalp.

7. Presence of single palmar crease.

8. Hernias are common in the affected individuals.

9. In males, the testicles are undescended (cryptorchidism).

10. In females, the uterus is bifurcated or branched (bicornuate uterus).

11. Hemangiomas are present on the skin surface (red or purplish birthmarks due to tiny vasculatures close to the skin).

What Are the Other Similar Conditions?

The genetic conditions that appear similar to trisomy 13 are:

• Edward’s syndrome or trisomy 18.

• Down syndrome or trisomy 21.

How to Diagnose Patau Syndrome?

This syndrome can be diagnosed prenatally or soon after birth. The following diagnostic tests may be essential in ruling out the syndrome. They are:

• Chorionic Villi Sampling- This test is usually done between 10 and 12 weeks of gestation. A sample of the placental tissue is taken and examined to detect any abnormalities in the growing fetus.

• Amniocentesis- The amniotic fluid that surrounds the baby in the uterus is taken and examined for the presence of any genetic conditions in the baby.

• Blood Investigations- It is a non-invasive prenatal test that detects the abnormalities seen in the baby's DNA that are present in the maternal blood.

• Fetal-Free DNA Analysis- It is a prenatal investigation where the genetic material of the mother and the baby is collected from the maternal blood. This test helps to rule out any genetic disorders such as trisomy 13, trisomy 18, and trisomy 21.

• Prenatal Ultrasounds- Trisomy 13 can be detected through ultrasound screenings from the 17th week onwards. They help to detect the abnormalities seen in the nervous system and cardiac and renal systems, facial deformities, etc. However, the ultrasound can only help to detect the possibilities of Patau syndrome. It does not provide 100 % accuracy.

• Tissue Microarray- This method detects genetic reasons that are responsible for fetal death.

• Physical Examination- Soon after birth, a thorough physical examination of the baby is done by the physician to identify any physical abnormalities. Sometimes the blood samples of the baby are also collected for lab investigations.

What Are the Possible Risk Factors and Complications?

Trisomy 13 is a life-threatening condition, and in severe cases, it is often fatal. It affects multiple organ systems such as the heart, kidney, liver, lungs, etc. 50 % of the affected individuals die before 20 weeks of gestation. About 90 % do not survive more than a year. Other complications seen in the affected babies include feeding problems, heart failure, epilepsy, and eyesight problems.

Can This Condition Be Prevented?

Researchers still do not understand the exact cause of the gene mutations, and there are no preventive measures for trisomy 13. However, the risk of the syndrome decreases if the age of mother is below 35 years. Although it is not an inherited condition, if there is any known family history, then prior genetic testing can be done.

How Can It Be Treated?

There is no definitive treatment for trisomy 13, and the treatment modalities are still controversial due to their poor prognosis. However, supportive treatment in the form of oxygen support or ventilation may be provided to the baby soon after birth. In some cases, surgeries may be required to treat the cleft lip and palate and correct the cardiac deformities. Despite these treatments, the children can only survive for an average of 733 days.

Conclusion:

There is no definitive treatment or possible ways to prevent this condition. Supportive therapy can only provide relief to the affected individual. Although a diagnosis of trisomy 13 in the baby can be upsetting for the parents, psychological counseling is advised to overcome the situation and take care of the baby. Patau syndrome is common in pregnant women over 35 years of age. Hence, regular prenatal checkups can help to detect the possibilities of genetic defects are mandatory.