Prader Willi Syndrome

Question 1

What is the genetic aetiology of PWS?

Answer 1

caused by absence of expression of the paternally active genes on the long arm of chromosome 15. The vast majority of cases occur sporadically.

Question 2

Any antenatal clues/

Answer 2

reduced fetal activity (later perception of movement, historically known as delayed quickening, as well as an overall reduction in the vigor of the movement), small size for gestational age, polyhydramnios, breech positioning, and asymmetrical intrauterine growth (increased head:abdomen circumference ratio)

Question 3

What are the clinical features in infancy?

Answer 3

Neonatal hypotonia is one of the hallmark features of this disorder and is a valuable clue to initiate diagnostic testing. The profound hypotonia can lead to asphyxia. Affected infants often have feeding difficulties, including a poor suck, which may lead to failure to thrive. Weak cry genital hypoplasia (eg, cryptorchidism, scrotal hypoplasia, or clitoral hypoplasia). Hypopigmentation of the skin, eyes (iris), and hair relative to the familial background is present in 30 to 50 percent of patients.

Question 4

What are the clinical features in early childhood?

Answer 4

late acquisition of major motor milestones (eg, average age for walking 27 months and for talking 39 months) Children between one and six years of age commonly manifest symptoms of hyperphagia with progressive development of obesity if access to food is unrestricted. Short stature is usually present during childhood and most patients fail to have a pubertal growth spurt. Most patients with PWS have growth hormone (GH) deficiency.