What is Prader-Willi syndrome?
Prader-Willi syndrome is a complex genetic condition. It occurs when there is lack of expression of one or more genes in a specific region on the chromosome 15 that was inherited from the father, the precise location of the abnormality being designated as 15(q11-q13). Various studies have shown that between 1 in 15,000 to 25,000 children are born with Prader-Willi syndrome and it affects all races and both sexes equally.
Signs and symptoms
There is usually a characteristic facial appearance with a narrow forehead, almond-shaped eyes, and a thin upper lip with downturned mouth. Scoliosis (S-shaped curvature of the spine) may also develop. Many individuals with Prader-Willi syndrome who have the deletion type have fairer colouring of their hair, eyes and skin compared to other family members. People with Prader-Willi syndrome typically have short stature compared to the family height and small hands and feet. Other symptoms include excessive appetite, incomplete sexual development, intellectual disability, irregularities in maintaining body temperature, temper outbursts and many more.
Children with Prader-Willi syndrome
The syndrome is marked by distinctly different presentations in infancy compared to childhood or later in life. Initially, a baby will present at birth with very low muscle tone resulting in a floppy baby (hypotonia), slightly low or normal birth weight and a poor suck. Subsequently there may be a failure to gain weight and grow well and delayed developmental milestones. Both boys’ and girls’ genitals are often poorly developed at birth, and one or both testes are usually undescended in males. The milestones of lifting the head, sitting up, crawling, walking, and speech all tend to be delayed. Excessive appetite combined with a lower than normal calorie requirement, and often the decreased physical activity related to the hypotonia, results in rapid weight gain.
Diagnosis of Prader-Willi syndrome
Prader-Willi syndrome is usually suspected on the basis of the clinical signs and symptoms and confirmed by genetic testing. Clinical diagnostic criteria have been published in the medical literature and confirmed as accurate.
Sources and useful links:
International Prader-Willi Syndrome Organisation
NORD – National Organization for Rare Disorders