What is Patau Syndrome?
Patau syndrome, also known as Trisomy 13, is a rare genetic disorder caused by the presence of an extra copy of chromosome 13. This genetic change leads to a variety of physical and cognitive abnormalities that are typical of the disorder.
Table of Contents
What is the cause of Patau Syndrome?
Patau syndrome, also known as Trisomy 13, is a genetic disorder caused by the presence of an extra copy of chromosome 13 in the cells of the body. Normally, humans have 23 pairs of chromosomes (46 in total), with one chromosome of each pair inherited from the mother and the other from the father. In Patau syndrome, there is an error during the formation of the egg or sperm cells, known as nondisjunction, which results in a reproductive cell carrying an extra copy of chromosome 13. When this cell contributes to the genetic material of the developing embryo, the result is three copies of chromosome 13 instead of the usual two. This additional genetic material disrupts normal development, causing severe physical and intellectual abnormalities.
There are three different forms of Patau syndrome, each caused by a variation in how the extra genetic material is present.
1. Full Trisomy 13: Every cell has an extra chromosome 13 (most common form).
2. Mosaic Trisomy 13: Some cells have the extra chromosome, others do not (less severe).
3. Translocation Trisomy 13: Part of chromosome 13 is attached to another chromosome (can be inherited).
The most common form of Patau syndrome is full Trisomy 13, which accounts for the majority of cases. In this form, every cell in the individual's body contains three complete copies of chromosome 13, instead of the usual two. This extra chromosome occurs due to an error known as nondisjunction during the formation of an egg or sperm cell. Nondisjunction happens when the chromosomes fail to separate properly during cell division, resulting in a gamete (reproductive cell) that carries an extra chromosome. When this gamete fuses with a normal one during fertilization, the resulting embryo ends up with a total of 47 chromosomes, including the extra chromosome 13. Full Trisomy 13 typically arises as a random and spontaneous event, meaning it is not inherited and does not usually recur in future pregnancies. However, maternal age is considered a risk factor, as the likelihood of nondisjunction increases with age.
A less common form is mosaic Trisomy 13, which occurs in only a small percentage of cases. In mosaicism, the extra chromosome 13 is present in only some of the cells of the body, while the rest have the normal number of chromosomes. This happens as a random error during one of the first few cell divisions after fertilization—after the embryo has already begun to develop. As a result, individuals with mosaic Trisomy 13 often exhibit a milder range of symptoms, depending on which organs and tissues are affected and the proportion of abnormal cells. For instance, if fewer critical organs have cells with the extra chromosome, the severity of physical and developmental issues may be reduced. However, even in mosaic cases, serious health challenges can still occur.
The third form is translocation Trisomy 13, which accounts for about 1–2% of cases. In this form, a piece or an entire copy of chromosome 13 becomes abnormally attached—or “translocated”—to another chromosome, before or at the time of conception. Unlike full Trisomy 13 or mosaicism, this form can sometimes be inherited from a parent who is a balanced translocation carrier. A balanced translocation means that a person carries rearranged genetic material between chromosomes, but all the necessary genetic information is still present, just in a different location. Therefore, the carrier does not have any symptoms or health problems. However, when this genetic material is passed on to a child, it can result in an unbalanced translocation, where the child inherits an extra portion of chromosome 13. This extra genetic material leads to the same types of developmental and physical problems seen in full Trisomy 13. Genetic counseling and chromosome analysis of the parents are especially important in translocation cases, as it can help determine recurrence risk in future pregnancies.
Overall, the primary cause of Patau syndrome is the presence of extra chromosome 13 material in the body’s cells, leading to abnormal development. While most cases are not inherited and occur sporadically, translocation forms can be passed from parent to child, making genetic counseling important for families who have had a child with this condition.
Features of Patau Syndrome
Patau syndrome, or Trisomy 13, is a severe chromosomal disorder characterized by a wide range of physical abnormalities, congenital malformations, and developmental challenges. The features and complications can vary between individuals, but several hallmark traits are commonly observed.
A. Physical Abnormalities of Patau Syndrome
Children born with Patau syndrome often present with distinctive physical features. These may include microcephaly (a small head), a small jaw and face, and microphthalmia (abnormally small eyes). In some cases, anophthalmia, or the complete absence of one or both eyes, may occur. A reduced distance between the eyes (hypotelorism) and abnormalities in the development of the nasal passages are also frequently seen.
Other common craniofacial anomalies include a cleft lip and/or cleft palate, which can affect feeding and speech development. Polydactyly, or the presence of extra fingers or toes, is a notable characteristic, often accompanied by syndactyly (webbing of the fingers or toes). The hands and feet may be clenched or malformed. Overall, the face tends to appear flat and small, and the body size is typically below average at birth.
B. Health Problems and Organ Malformations in Patau Syndrome
Children with Patau syndrome are prone to a variety of serious health issues, many of which can be life-threatening:
1. Heart Defects
Congenital heart abnormalities are among the most common and severe complications in Patau syndrome. These include:
➤ Ventricular Septal Defect (VSD): A hole in the wall separating the lower chambers of the heart, allowing oxygen-rich and oxygen-poor blood to mix.
➤ Atrial Septal Defect (ASD): A similar defect affecting the upper heart chambers.
➤ Patent Ductus Arteriosus (PDA): A persistent fetal blood vessel that should close after birth, but remains open, straining the heart and lungs.
➤ Dextrocardia: A condition in which the heart is located on the right side of the chest.
➤ Transposition of the Great Arteries: The two main arteries leaving the heart are reversed, affecting oxygenation.
➤ Coarctation of the Aorta: A narrowing of the aorta, leading to reduced blood flow to the body.
These cardiac conditions often require surgical intervention, though the presence of multiple anomalies can make treatment complex.
2. Breathing Problems
Many infants have structural abnormalities in the nose, airway, or lungs that make breathing difficult. These issues may contribute to respiratory infections and chronic oxygen deficiency.
3. Vision and Hearing Problems
Visual impairments such as cataracts, strabismus (crossed eyes), and structural eye anomalies are common. Hearing loss is also frequently observed, resulting from inner ear malformations or frequent infections.
4. Neurological Issues
Due to abnormal brain development, seizures are common in individuals with Patau syndrome. Structural defects such as holoprosencephaly—a failure of the brain to divide properly into hemispheres—may also be present and contribute to severe developmental delays.
5. Feeding Difficulties
Many newborns struggle to feed due to oral structural defects (like cleft palate), weak suck reflexes, and difficulty swallowing (dysphagia). These problems may necessitate the use of feeding tubes.
6. Growth and Developmental Delays
Children with Patau syndrome typically exhibit significant delays in achieving developmental milestones. Motor skills, cognitive development, and communication abilities are all profoundly affected. Many affected individuals require lifelong support for basic functions.
Prognosis and Survival
Sadly, Patau syndrome is one of the most severe and life-limiting chromosomal disorders. More than 50% of affected newborns die within the first week of life, and over 90% do not survive beyond the first year. The high mortality rate is due to the presence of multiple, complex congenital anomalies, especially those affecting the heart and brain.
Variation Among Individuals
It is important to note that the severity and range of symptoms can differ depending on the type of Trisomy 13 (full, mosaic, or translocation), the specific organs involved, and how the individual responds to supportive care. Some children with mosaic or translocation Patau syndrome may live longer and show milder symptoms, though they still face significant challenges.
Diagnosis of Patau Syndrome
Patau syndrome, also known as Trisomy 13, is a severe chromosomal condition caused by the presence of an extra copy of chromosome 13. The diagnosis of this syndrome can be made either prenatally (before birth) or postnatally (after birth) through a variety of clinical and genetic testing methods. Early and accurate diagnosis is crucial for informed decision-making, medical management, and support for the family.
A. Prenatal Diagnosis of Patau Syndrome
Prenatal diagnosis of Patau syndrome typically begins with routine screening tests conducted during pregnancy. These tests assess the risk of chromosomal abnormalities, including Trisomy 13, and are followed by diagnostic tests if abnormalities are suspected.
1. First-Trimester Screening
This screening includes a combination of ultrasound and maternal blood tests, usually performed between the 11th and 14th weeks of pregnancy. The ultrasound may detect physical abnormalities associated with Patau syndrome such as holoprosencephaly (incomplete separation of the brain), increased nuchal translucency (fluid at the back of the fetus’s neck), or major structural defects. Blood tests measuring levels of specific proteins and hormones (e.g., PAPP-A and hCG) may also indicate a higher risk.
2. Non-Invasive Prenatal Testing (NIPT)
NIPT is a highly accurate blood test that analyzes cell-free fetal DNA circulating in the mother's bloodstream. This test can detect the presence of an extra chromosome 13, and while it is a screening test (not diagnostic), it has a very high sensitivity and specificity. It can be done as early as the 10th week of pregnancy.
3. Confirmatory Diagnostic Tests
If a screening test indicates a high risk of Trisomy 13, confirmatory tests are recommended. These include:
➧ Chorionic Villus Sampling (CVS): Performed between the 10th and 13th weeks of pregnancy, this test involves taking a small sample of placental tissue to analyze the chromosomes.
➧ Amniocentesis: Usually done between the 15th and 20th weeks, this procedure involves extracting a sample of amniotic fluid surrounding the fetus to examine fetal cells for chromosomal abnormalities.
Both CVS and amniocentesis carry a small risk of miscarriage but provide a definitive diagnosis by analyzing the fetal karyotype.
B. Postnatal Diagnosis of Patau Syndrome
If Patau syndrome is not diagnosed prenatally, it can often be suspected at birth due to the presence of distinctive physical abnormalities. A full diagnostic evaluation follows to confirm the condition.
1. Physical Examination
Doctors may recognize Patau syndrome in a newborn based on characteristic features such as cleft lip or palate, polydactyly (extra fingers or toes), microphthalmia (small eyes), low-set ears, scalp defects, and congenital heart defects. However, since these signs can also occur in other conditions, a genetic test is necessary for confirmation.
2. Karyotype Analysis
This is the most definitive test for diagnosing Patau syndrome. A sample of the baby’s blood is analyzed to produce a karyotype, which reveals the number and structure of chromosomes. In full Trisomy 13, the karyotype will show three copies of chromosome 13 in every cell.
In mosaic Trisomy 13, only a portion of the cells carry the extra chromosome, so multiple cell samples may be needed to detect it accurately. In translocation Trisomy 13, part or all of chromosome 13 is attached to another chromosome, and additional testing may be required to determine whether this form is inherited from a parent.
C. Additional Diagnostic Evaluations for Patau Syndrome
Once a diagnosis of Patau syndrome is confirmed, additional tests are typically ordered to assess the extent of organ involvement and to help guide medical management. These include:
➧ Echocardiography to detect heart defects.
➧ Brain imaging (MRI or ultrasound) to identify structural brain abnormalities.
➧ Hearing and vision assessments to evaluate sensory impairments.
➧ Renal ultrasound to check for kidney malformations.
Genetic Counseling about Patau Syndrome
When Patau syndrome is diagnosed, whether prenatally or postnatally, genetic counseling is highly recommended for the family. Genetic counselors help explain the nature of the condition, recurrence risk in future pregnancies, and available support resources. In cases involving translocation Trisomy 13, parental chromosomal analysis is important to determine whether a parent is a balanced carrier of a translocation, which can affect future reproductive planning.
The diagnosis of Patau syndrome involves a combination of screening, clinical observation, and confirmatory genetic testing. With advances in prenatal screening technologies, such as NIPT, many cases can now be identified early in pregnancy, allowing families more time to prepare for care decisions. Postnatal diagnosis is essential for appropriate medical intervention and support. Accurate diagnosis also plays a critical role in counseling families and ensuring the best possible outcomes in terms of management and emotional support.(alert-passed)
Management for Patau Syndrome
Patau syndrome, also known as Trisomy 13, is a severe chromosomal disorder that results in multiple congenital abnormalities and serious health complications. Management of this condition is complex and highly individualized, focusing primarily on providing comfort, treating life-threatening medical issues, and supporting both the child and their family. There is no cure for Patau syndrome, so care is typically palliative or supportive, though some children with less severe presentations may receive life-prolonging treatments.
A. Initial Assessment and Stabilization
Immediately after birth, a child suspected of having Patau syndrome requires a thorough medical evaluation. This includes a physical examination to assess congenital abnormalities, and diagnostic imaging (such as echocardiography, cranial ultrasound, and abdominal ultrasound) to identify internal organ malformations. Stabilizing the newborn is the first priority—this may involve respiratory support if breathing is compromised, and nutritional assistance if feeding is difficult due to cleft lip/palate or low muscle tone.
B. Multidisciplinary Medical Management of Patau Syndrome
Due to the wide range of health issues associated with Patau syndrome, a multidisciplinary team is essential. This team often includes neonatologists, cardiologists, neurologists, geneticists, ophthalmologists, audiologists, nutritionists, and palliative care specialists. Management plans are developed based on the individual child’s specific conditions and complications.
1. Cardiovascular Management
Congenital heart defects are present in over 80% of cases. These may include ventricular septal defects, atrial septal defects, patent ductus arteriosus, and more severe conditions such as transposition of the great arteries. In some cases, surgical repair may be considered if the child is stable and the defects are operable. However, in many situations, supportive treatment (such as oxygen therapy and medications) is preferred due to the overall poor prognosis.
2. Neurological and Seizure Management
Many children with Patau syndrome have structural brain abnormalities, such as holoprosencephaly, which can lead to seizures and developmental delays. Neurological support includes the use of anti-seizure medications, close monitoring of neurological function, and referrals to pediatric neurologists.
3. Respiratory and Feeding Support
Breathing difficulties are common due to facial malformations, underdeveloped lungs, or muscle hypotonia. Some infants may require mechanical ventilation or tracheostomy in severe cases. Feeding difficulties due to cleft palate or poor sucking ability may necessitate tube feeding (e.g., via a nasogastric tube or gastrostomy).
C. Supportive and Palliative Care for Infants with Patau Syndrome
For most infants with full Trisomy 13, the prognosis is extremely poor, with many not surviving beyond the first few weeks of life. In such cases, palliative care becomes the focus, aiming to ensure comfort and dignity. Palliative teams help manage pain, minimize suffering, and support families through complex emotional and ethical decisions regarding medical interventions.
D. Developmental Support for Survivors of Patau Syndrome
In rare cases, especially in children with mosaic or partial Trisomy 13, survival beyond infancy is possible, and developmental support becomes a greater priority. These children may benefit from:
➧ Physical therapy to improve motor skills
➧ Occupational therapy to aid in daily living tasks
➧ Speech and language therapy for communication and feeding issues
➧ Special education services tailored to cognitive limitations
Although developmental progress is usually limited and slow, early intervention can help maximize the child’s potential.
E. Family and Psychosocial Support
Caring for a child with Patau syndrome is emotionally and physically demanding. Families require psychological support, genetic counseling, and access to social services. Counseling helps parents understand the condition, make informed decisions, and cope with grief or ongoing stress. In cases involving translocation Trisomy 13, parental chromosomal testing is advised to evaluate recurrence risk in future pregnancies.
Support groups, respite care services, and community resources also play a critical role in helping families manage the challenges of caring for a child with special needs.
F. Ethical and End-of-Life Considerations for Patau Syndrome
Decisions regarding intensive interventions (like surgery or prolonged ventilation) can be ethically complex. Healthcare providers should have open, compassionate discussions with families about the child’s prognosis, quality of life, and available options. Respecting family values and preferences while providing clear medical guidance is essential in developing a care plan that aligns with the family’s goals.
It's important to note that the management of Patau Syndrome is highly individualized and will depend on the specific health problems and complications present in each affected individual. A healthcare provider can provide more information on the available treatment options and help develop a personalized care plan based on the individual's needs and circumstances.
Managing Patau syndrome involves a balance between medical intervention and compassionate care. While survival is limited in most cases, the quality of life for the child and family can be improved through comprehensive, coordinated care. Whether the approach is palliative or includes certain corrective interventions, the focus remains on ensuring comfort, dignity, and meaningful support for both the child and their loved ones.(alert-passed)
Prognosis of Patau Syndrome
Patau Syndrome, or Trisomy 13, is a rare and severe chromosomal disorder caused by the presence of an extra copy of chromosome 13 in some or all of a person's cells. The prognosis for individuals with this condition is generally poor, largely due to the complex and often life-threatening congenital abnormalities that affect multiple organ systems. While survival rates have improved slightly due to advances in neonatal care and early medical intervention, Patau Syndrome remains one of the most serious genetic syndromes diagnosed in infancy.
Survival Rates of Infants with Patau Syndrome
The survival rate for infants with Patau Syndrome is extremely low. It is estimated that more than 50% of babies with Trisomy 13 die within the first week of life, and about 90% do not survive past their first year. Most deaths occur due to severe congenital heart defects, respiratory complications, or neurological abnormalities that are present at birth. Despite medical advancements, the underlying genetic abnormality cannot be cured, and treatments often focus on managing symptoms rather than correcting the condition itself.
Factors Influencing the Prognosis of Patau Syndrome
The prognosis for a child with Patau Syndrome can vary based on several factors, including the type of Trisomy 13, the severity of malformations, and the availability of supportive care.
Full Trisomy 13 (the most common type) is typically associated with the worst outcomes, as all cells in the body carry the extra chromosome, leading to widespread defects.
Mosaic Trisomy 13, where only some cells have the extra chromosome, can result in milder symptoms, and affected individuals may live longer—sometimes into childhood or even adolescence—depending on how many cells are involved and which organs are affected.
Translocation Trisomy 13 may also be associated with a slightly better prognosis if only part of the chromosome is duplicated, though this still typically results in significant medical challenges.
In addition, the quality and timeliness of medical care, such as early diagnosis, surgical intervention for heart defects, and supportive therapies, can influence the child’s quality of life and survival.
Medical Complications Affecting Prognosis
The high mortality associated with Patau Syndrome is largely due to multiple organ system abnormalities, including:
1. Congenital heart defects, such as ventricular septal defects, atrial septal defects, and patent ductus arteriosus, which can severely impair blood circulation and oxygen delivery.
2. Central nervous system abnormalities, including holoprosencephaly, which affects brain development and function.
3. Cleft lip and/or palate, feeding difficulties, and breathing problems that increase the risk of aspiration, malnutrition, and infections.
4. Kidney and urogenital abnormalities which may impair waste removal and fluid balance.
5. Severe developmental delays and intellectual disabilities, which hinder the ability to communicate and learn.
These complications often occur together and are difficult to treat comprehensively, especially in the fragile early months of life.
Long-Term Outlook for Survivors
While long-term survival is rare, a small number of children with mosaic or partial Trisomy 13 do survive past infancy. These individuals often face profound developmental delays, cognitive impairment, motor difficulties, and significant health challenges. Most require lifelong medical care, physical therapy, and educational support. Speech may be limited or absent, and many children remain nonverbal and dependent on caregivers for daily tasks.
However, despite these challenges, some children with milder forms of Trisomy 13 can form emotional bonds with family members and may develop limited functional skills. With a strong support system, specialized care, and therapy, these children can experience a meaningful quality of life, though still with significant disabilities.
Psychosocial and Emotional Considerations for Families
Receiving a diagnosis of Patau Syndrome can be emotionally devastating for families. The knowledge of a poor prognosis and the likelihood of early mortality bring intense grief, fear, and anxiety. Families are often faced with complex decisions regarding the extent of medical interventions, such as whether to pursue life-sustaining surgeries or focus on palliative care.
Genetic counseling is essential for helping families understand the diagnosis, the likelihood of recurrence in future pregnancies, and their reproductive options. Additionally, psychosocial support and grief counseling can help families navigate the emotional burden associated with caring for a child with such a severe condition or coping with early loss.
