PWS: Prader-Willi Syndrome - Article Example

Neonatal and infants show lethargy, poor reflexes, feeding, sucking problems and poor weight gain. PWS has an incidence of 1 in 10,000-29,000 people worldwide (Yearwood et al., 2011) while in U.S. its occurrence is reported to be1 per 16,000-25,000 population (Butler, 1996). It is prevalent in all races and both genders. Cassidy and Driscoll (2009) have reported an estimated death rate of 3% per year in a population study. Research suggests frequent causes of death in PWS patients (approx 60%) are cardiovascular disorders and stroke along with complications related to obesity, respiratory disorders, shock pneumonia and hypoventilation (Yearwood et al., 2011). PWS is a consequence of abnormalities of imprinted region of proximal 15q.

Research suggests an uncertain relationship between genetics and clinical signs of PWS. It can arise from either paternal or maternal factors however; around 70% of the cases are attributed to paternal inheritance involving a missing gene from chromosome 15 in areas of 15q11-q13. 20% of the cases occur due to maternal uniparental disomy i.e. . These include FISH (fluorescence in situ hybridization) which identifies deletions, translocations, chromosomal alterations etc, High resolution chromosomal analysis test which is helpful in detection of chromosomal deletions, abnormalities, translocations and DNA methylation analysis which detects imprinting patterns and DNA polymorphism and is commonly used (99% of the cases) for accurate diagnosis for PWS.

Differential DNA methylation of specific maternal and paternal alleles in 15q11-13 chromosomal region evaluates inheritance source of the disease such as paternal only, maternal and biparental (Cassidy and Driscoll 2009). DNA methylation confirms all three molecular classes along with distinguishing PWS from closely related Angelman syndrome in affected individuals. Central nervous system is majorly affected by this disease in particular hypothalamus. The development of central nervous system takes place as early as 3rd week in embryo in the form of neural tube with hypothalamus forming at 5th week.

Later hypothalamus modifies and develops to form a hypothalamic endocrine axes responsible for the secretion of hormones. Characteristic GH insufficiency in PWS patients is attributed to hypothalmic dysfunction (Yearwood et al., 2011). This process continues after birth. Lungs, liver, intestinal tract and kidney also start to develop at the same time in embryo. Decreased fetal movement, abnormal fetal heart rhythm, polyhydramnios, breech or mal-presentation may lead to suspected prenatal screening of PWS however; prenatal diagnosis is rarely done (Cassidy and Driscoll, 2009).

Prenatal screening of PWS involves FISH by samples obtained from chorionic villus sampling or amniocentesis. Detection of trisomy 15 or deletions on CVS through FISH analysis should