Patients with Angelman syndrome (AS) symptoms harboring MECP2 mutations are classified as AS patients in the Online Mendelian Inheritance in Man /OMIM database of the U.S. National Center for Biotechnology Information (Phenotype MIM number 105830)

Thanks Anne,

The phonotypes of Rett Syndrome and Angelman, however, are quite similar in many cases. How does one differentiate between the two syndromes.

Angelman syndrome (AS) is a distinct neurogenetic syndrome, first described in 1965. The phenotype is well known in infancy and adulthood, but the clinical features may change with age. The main clinical characteristics include severe mental retardation, epileptic seizures and EEG abnormalilties, neurological problems and distinct facial dysmorphic features. Behavioural problems such as hyperactivity and sleeping

problems are reported, although these patients present mostly a happy personality with periods of inappropriate laughter.

http://www.opleiding-jgz.be/bestanden/2009-2010/Angelman%20syndrome.pdf

Angelman syndrome is related to 15q11.2. OMIM reports a Angelman Syndrom-like related to Xp22.13

 I would say that they are cases of Rett syndrome that were misdiagnosed as Angelman syndrome that has a similar phenotype. I have come across such cases.

I am not a physician and thus don't know how difficult it is to establish a differential diagnosis for AS.

However if this is feasible for you Dick, Angelman/Rett Syndrome genetic testing panels are now available from various sources. This would give you a definitive answer.

Anne, I think the issue is because these syndromes were established on the basis of signs and symptoms (phenotype) but now with genetic testing, we are gradually relying more on genotypes (what the individual's DNA says). This is a more reliable measure, especially in cases where phenotypes overlap, but we are reluctant to let go of the old system. So perhaps the question should be "should we abandon the old system of relying on symptoms once reliable genetic tests provide a more reliable way to categorize patients?"

A genetic diagnostic is not crucial right now since no effective disease therapies are available. Most of the time symptoms are enough to establish a reliable diagnosis. However genetic testing will be a must once disease/mutations specific treatments become available (this is the new approach in drug discovery. So why not start right now?

Anne, I agree with you about the lack of specific treatments based on genetic diagnoses, but there are some reasons that it is also helpful to begin to sort out the overlapping phenotypes for other reasons. For example, some therapies may be more helpful for some conditions than others, and certain health problems may be identified earlier if we know the correct diagnosis. It is also useful for clinical research since treatments may be more effective with some genetic conditions than others.