Schaaf-Yang syndrome (SHFYNG)

What is Schaaf-Yang syndrome?

It is a rare genetic syndrome that is similar to Prader-Willi syndrome. It shares similar symptoms with the syndrome but minus the excessive appetite that accompanies Prader-Willi.

This syndrome is also known as:
Prader-willi-like Syndrome; PWLS; Arthrogryposis, Distal, with Hypopituitarism, Mental Retardation, and Facial Anomalies; Chitayat-Hall syndrome

What gene changes cause Schaaf-Yang syndrome?

Mutations to the MAGEL2 gene on chromosome 15 cause the syndrome.
If this gene, along with several other genes, is missing it causes Prader-Willi syndrome. This is usually inherited in an autosomal dominant pattern, but most cases of the syndrome are de novo or new mutations.

In the case of autosomal dominant inheritance just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it onto each of their children. Syndromes inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation.

In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation which occurs during the reproductive process.

What are the main symptoms of Schaaf-Yang syndrome?

The main symptoms of the syndrome, in infants especially, include low muscle tone as well as difficulties with feeding.

Developmental delay, intellectual disability and autism spectrum disorder are also associated with the syndrome.

Affected individuals may also have joint contractures- this usually involves permanently bent or permanently straightened joints in the finger. This can also affect the knees and elbows too.

Possible clinical traits/features:
Hypogonadism, Polyphagia, Global developmental delay, Short stature, Autosomal dominant inheritance, Seizure, Obesity, Open mouth, Micropenis, Neonatal hypotonia, Narrow forehead, Narrow palm, Myopia, Intellectual disability, Cryptorchidism, Flexion contracture, Coarse facial features, Constipation, Feeding difficulties in infancy, Failure to thrive in infancy, Esotropia, Sleep apnea, Small hands.

How is Schaaf-Yang syndrome diagnosed?

To find out if someone has a diagnosis of Schaaf-Yango syndrome, it is important to have a consultation and evaluation with a clinical genetic specialist.  Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis.  FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.