Patau syndrome

Overview

Patau syndrome, also known as trisomy 13, is a severe genetic disorder caused by the presence of an extra copy of chromosome 13 in some or all of the body's cells. First described by Dr. Klaus Patau in 1960, this condition results in profound intellectual disability, numerous congenital malformations, and serious medical complications. It is one of the most severe forms of trisomy and affects approximately 1 in 10,000 to 16,000 live births. The majority of infants with Patau syndrome do not survive beyond the first few weeks of life due to the seriousness of their medical conditions. Despite its rarity, the condition is a critical focus in prenatal diagnostics due to its high mortality and complex clinical presentation.

Causes

Patau syndrome is primarily caused by trisomy of chromosome 13, meaning there are three copies of chromosome 13 instead of the usual two. This extra genetic material disrupts normal development and leads to multiple system abnormalities. The three main types of Patau syndrome include:

• Full Trisomy 13: All cells in the body contain an extra chromosome 13. This is the most common and severe form.

• Mosaic Trisomy 13: Only some cells have the extra chromosome, while others have the normal two copies. This form may have milder symptoms.

• Translocation Trisomy 13: Part of chromosome 13 is attached to another chromosome. This can be inherited from a parent who is a balanced carrier.

Most cases of Patau syndrome are not inherited but occur as random events during the formation of reproductive cells, especially in older mothers.

Symptoms

The symptoms of Patau syndrome are extensive and usually affect multiple organ systems. Common features include:

• Severe intellectual disability

• Microcephaly (small head size)

• Holoprosencephaly (failure of the brain to divide properly)

• Cleft lip and/or cleft palate

• Polydactyly (extra fingers or toes)

• Low-set or malformed ears

• Small or poorly developed eyes (microphthalmia)

• Congenital heart defects (e.g., ventricular septal defect, atrial septal defect)

• Renal abnormalities, including polycystic kidneys

• Hypotonia (reduced muscle tone)

• Scalp defects (cutis aplasia)

• Severe growth retardation

Infants with Patau syndrome often present with breathing difficulties and feeding challenges from birth.

Diagnosis

Diagnosis of Patau syndrome can be made during pregnancy or after birth. The primary diagnostic steps include:

• Prenatal screening: Non-invasive blood tests such as cell-free fetal DNA testing can suggest the presence of trisomy 13.

• Ultrasound: May detect abnormalities such as heart defects, brain malformations, or facial anomalies during pregnancy.

• Definitive prenatal diagnosis: Procedures like chorionic villus sampling (CVS) or amniocentesis allow karyotyping of fetal cells to confirm the diagnosis.

• Postnatal diagnosis: Physical examination combined with chromosomal analysis (karyotype or FISH) confirms the presence of an extra chromosome 13.

Due to the severity of symptoms, many cases are identified shortly after birth if not detected prenatally.

Treatment

There is no cure for Patau syndrome, and treatment is focused on supportive care and symptom management. Decisions about medical intervention often depend on the severity of anomalies and the goals of the family. Key treatment approaches include:

• Neonatal intensive care: For immediate stabilization of breathing and feeding

• Surgical interventions: May be considered for correctable defects such as cleft lip/palate or certain heart anomalies, though often limited due to poor overall prognosis

• Feeding support: Including nasogastric or gastrostomy tubes for nutrition

• Palliative care: Focused on comfort, pain management, and family support in severe cases

• Developmental therapy: For children who survive beyond infancy, physical, occupational, and speech therapy may help improve quality of life

Many families work closely with a palliative care team to make decisions that align with their values and the child’s quality of life.

Prognosis

The prognosis for individuals with Patau syndrome is generally poor. Over 80% of affected infants die within the first month of life, and less than 10% survive beyond their first year. Survivors often have profound physical and intellectual disabilities and require lifelong care. Mosaic or translocation forms of the condition may have a milder course, but significant health challenges are still common. Supportive care, early diagnosis, and compassionate family-centered care are essential components in managing this condition. Genetic counseling is highly recommended for families who have had a child with Patau syndrome, especially in cases involving translocations.