Phase I is the prenatal, neonatal, and early infancy period. During this period the child shows diminished fetal activity, poor muscle tone, and a failure to thrive after birth. Phase II is between the ages of two and three. During this phase uncontrollable hunger emerges. During the 1970's and 1980's literature described the behavioral, personality, and medical problems associated with PWS. A study by Greenswag in 1987 showed that a controlled diet can extend the life expectancy of individuals with PSW. Greenswag's study also showed that emotional lability does increase with age and is independent of the presence of adult obesity.
Now that we know a little bit of history about Prader-Willi Syndrome, let's look at the three main genetic errors that cause Prader-Willi Syndrome. The most common of these errors is a non-inherited deletion in the paternally contributed chromosome 15. This type of genetic error is the cause of seventy percent of Prader-Willi Syndrome cases. The second most common genetic error that causes PSW is maternal uniparental disomy. This occurs when both chromosome 15s are inherited by the mother. About twenty-five percent of PWS cases are caused by maternal uniparental disomy. Lastly, an imprinting defect inherited from the father will not allow the normal expression of the active genes on chromosome 15. .
Scientists and physicians are discovering more and more about Prader-Willi Syndrome and how to read the genetic structure that can lead to a child developing this syndrome. It is important to know some of the common characteristics of an individual with Prader-Willi Syndrome. Let start by talking about some of the Major Clinical Findings.
