First described by Klaus Patau in 1960, Patau syndrome, also known as Trisomy 13, is a rare and severe chromosomal disorder caused by the presence of an extra copy of chromosome 13. Normally, humans have 46 chromosomes, arranged in 23 pairs. However, individuals with Patau syndrome possess 47 chromosomes due to the triplication of chromosome 13.
Mechanisms of Chromosomal Abnormalities
Nondisjunction: The primary mechanism leading to Patau syndrome is nondisjunction, where chromosome pairs fail to separate properly during the formation of egg or sperm cells. This results in an egg or sperm cell with an extra chromosome 13.
Translocation: In some cases, Patau syndrome can result from a translocation, where a portion of chromosome 13 attaches to another chromosome. This can be a balanced translocation in a parent (without symptoms) that becomes unbalanced in the offspring.
Mosaicism: Rarely, Patau syndrome can occur in a mosaic form, where only some cells have the extra chromosome 13. This happens due to a nondisjunction event occurring in one of the initial cell divisions after fertilization.
Clinical Features of Patau Syndrome
Patau syndrome is associated with severe physical and developmental abnormalities. Common features include:
Craniofacial Abnormalities: Individuals often exhibit microcephaly (small head size), holoprosencephaly (failure of the brain to divide properly), cleft lip and/or palate, and low-set ears.
Cardiac Defects: Congenital heart defects are present in about 80% of cases, including ventricular septal defects, atrial septal defects, and patent ductus arteriosus.
Ocular Abnormalities: Structural eye defects such as microphthalmia (small eyes) or anophthalmia (absence of one or both eyes) are common.
Polydactyly: Extra fingers or toes.
Growth Retardation: Significant delays in growth and development.
Neurological Impairments: Severe intellectual disability and motor skill deficits.
The prognosis for individuals with Patau syndrome is poor, with many affected infants not surviving past the first few weeks or months of life. However, some children do survive longer, with varying degrees of medical and developmental support.
Techniques of Diagnosis
Early and accurate diagnosis of Patau syndrome is crucial for appropriate medical management and family counseling. Several diagnostic techniques are employed, ranging from prenatal screening (Ultrasound, NIPT, Amniocentesis and CVS) to postnatal confirmation (Physical examination of features, karyotyping, FISH, aCGH).
Genetic Counseling and Management
Genetic counseling plays a vital role in managing Patau syndrome. Counselors provide families with information about the condition, discuss the risks of recurrence in future pregnancies, and support decision-making processes regarding prenatal testing and pregnancy management.
Management of Patau syndrome is complex and requires a multidisciplinary approach. Medical interventions focus on addressing the immediate health challenges, such as congenital heart defects and feeding difficulties. Long-term care involves supportive therapies, including physical, occupational, and speech therapy, to optimize the child's development and quality of life.
The diagnosis of Patau syndrome presents significant ethical considerations. Prenatal testing raises questions about the potential for selective termination of affected pregnancies. Families face challenging decisions that must be guided by personal values, beliefs, and comprehensive medical information. Healthcare providers must offer empathetic support and respect the autonomy of the family in making these decisions.
-Written by Sohni Tagore
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