A new study sheds light on the clinical characteristics of Schaaf-Yang Syndrome in adults. In addition to other important findings, the study suggests there is more overlap between PWS and Schaaf-Yang Syndrome than previously understood, and confirms that a diagnosis of Schaaf-Yang Syndrome should be considered for all adults that are suspected of having PWS, if genetic testing for PWS is negative.
About Schaaf-Yang Syndrome
Schaaf-Yang Syndrome is a rare disorder caused by a mutation in one of the PWS-region genes, MAGEL2. Dr. Christian Schaaf led the work that first described SHFYNG in the medical literature in 2013 and continues to work with a growing group of Schaaf-Yang Syndrome patients and families to better characterize this disorder.
In a study published in 2015 looking at PWS and Schaaf-Yang Syndrome, Dr. Schaaf and colleagues found that the two share some clinical features such as:
- hypotonia (low muscle tone) and poor suck/feeding difficulties in childhood
- hypogonadism (incomplete puberty)
- growth hormone deficiency
- intellectual disability
However, there were some unique features as well, including:
- in Schaaf-Yang Syndrome: short and stiff finger joints at birth and autism
- in PWS: severe early hyperphagia (excessive appetite), characteristic facial features, and obesity
The 2015 study and others have described the clinical characteristics for children with Schaaf-Yang Syndrome, but there has not been much information available on the clinical characteristics for adults with Schaaf-Yang Syndrome.
New Schaaf-Yang Syndrome Findings
In the new study, published in the Orphanet Journal of Rare Diseases, Dr. Schaaf and his colleagues have studied in detail 7 adults (aged 18-36 years old) with confirmed Schaaf-Yang Syndrome, learning more about their clinical and behavioral features.
Overall, the researchers found that in these adults with Schaaf-Yang Syndrome, there was a very high variability in functional abilities, skills, and social functioning. The adult phenotypes in Schaaf-Yang Syndrome include:
- sleep disturbances with excessive daytime sleepiness
- intellectual disability
- hypotonia
- constipation
- hypogonadism
- autism
The degree of intellectual disability varied among the participants but was most often in the "mild" range, and the degree of independence considerably among the individuals. Several individuals participated in sports activities and were able to work in protected environments, while others were primarily dependent on others for care. Furthermore, this research showed that the characteristics of Schaaf-Yang Syndrome in adults more closely mirrors the phenotype (characteristics) of PWS (especially in adulthood), as compared to the description of children with Schaaf-Yang Syndrome published in 2015. Notably, in these adults with Schaaf-Yang Syndrome, hyperphagia (overeating and food seeking behaviors) as well as excessive weight gain / obesity were common. There were also some behavioral features that were similar to those often found in PWS, including anxiety, repetitive behaviors and sometimes obsessive interests.
Given that both the current study and the study published in 2015 included relatively small numbers of individuals with Schaaf-Yang Syndrome, assessed at one point in time, it’s not yet clear if the differences in characteristics seen in children compared to adults with Schaaf-Yang Syndrome is a true difference, or more related to the wide variability in the phenotype of Schaaf-Yang Syndrome.
Nonetheless this study suggests there is more overlap between PWS and Schaaf-Yang Syndrome than previously understood. It also confirms that a diagnosis of Schaaf-Yang Syndrome should be considered for all adults that are suspected of having PWS, if genetic testing for PWS is negative. Finally, the paper adds to our growing knowledge of the scope of features and variability in Schaaf-Yang Syndrome syndrome, which may be helpful for families navigating life with Schaaf-Yang Syndrome.
