Prader-Willi Syndrome – Genetic Disorder That Cause Obesity

Prader-Willi syndrome or PWS syndrome is thought to be one of the most common genetic disorders. Prader-Willi syndrome and Angelman syndrome were the first examples in humans of genomic imprinting in Cytogenetics. Angelman syndrome has an entirely different clinical condition with PWS syndrome. I will explain about the Angelman syndrome in my future post.

What is genomic imprinting? Imprinting is a type of marking process that has a memory. Genomic imprinting is where a segment of DNA is marked or imprinted during gametogenesis. This mark will be retained and recognized throughout the life of the individual. Maternal and paternal inherited alleles will be marked differently and are expressed differently in the offsprings. Therefore, the offspring with the same genetic material will have different appearances. The individual with Prader-Willi syndrome is because the loss of paternally inherited region 15q11 – q13 of chromosome 15. Simple to say, the PWS individual does not inherit the region 15q11 – q13 of chromosome 15 from his/her father but only from mother.

Prader-Willi syndrome is the most common genetic cause of marked obesity in humans according to Cytogenetics. It is a complex disorder with cardinal features of

i) Infantile hypotonia (low muscle tone)

ii) Mild growth retardation

iii) Frequent occurrence of breech presentation (baby enters the birth canal with the buttocks or feet first)

iv) Small hands and feet with gracile and tapering fingers

v) Microcephaly (smaller head)

vi) Almond-shaped eyes

vii) Mental deficiency (average IQ of 65)

viii) Short stature and so on.

From the age of about one and half years onward, hyperphagia becomes a serious problem, leading to gross obesity. Due to hyperphagia and gross obesity, diabetes often sets in during adolescence or later. Epilepsy is found in a minority of cases. Mental development is characterised by moderate to severe retardation with tendency to behaviour disorders, especially reactive to food deprivation. Patients with this syndrome may need specialists for assessment and treatment of their behavioural and learning problems, at the beginning of childhood. Prader-Willi syndrome is present in all races and ethnic groups and most cases are sporadic.

In conclusion, Prader-willi syndrome is a genetic disorder that needs treatment and assessment to overcome the learning problem and obesity problem of the patients. I will write a series of Prader-Willi syndrome in this Cytogenetics and Cancer Research blog in order to give people a clear mind about this syndrome. Stay tuned!