Schaaf-Yang syndrome overview: Report of 78 individuals

John McCarthy, Philip J. Lupo, Erin Kovar, Megan Rech, Bret Bostwick, Daryl Scott, Katerina Kraft, Tony Roscioli, Joel Charrow, Samantha A. Schrier Vergano, Edward Lose, Robert Smiegel, Yves Lacassie, Christian P. Schaaf*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Schaaf-Yang Syndrome (SYS) is a genetic disorder caused by truncating pathogenic variants in the paternal allele of the maternally imprinted, paternally expressed gene MAGEL2, located in the Prader-Willi critical region 15q11-15q13. SYS is a neurodevelopmental disorder that has clinical overlap with Prader-Willi Syndrome in the initial stages of life but becomes increasingly distinct throughout childhood and adolescence. Here, we describe the phenotype of an international cohort of 78 patients with nonsense or frameshift mutations in MAGEL2. This cohort includes 43 individuals that have been reported previously, as well as 35 newly identified individuals with confirmed pathogenic genetic variants. We emphasize that intellectual disability/developmental delay, autism spectrum disorder, neonatal hypotonia, infantile feeding problems, and distal joint contractures are the most consistently shared features of patients with SYS. Our results also indicate that there is a marked prevalence of infantile respiratory distress, gastroesophageal reflux, chronic constipation, skeletal abnormalities, sleep apnea, and temperature instability. While there are many shared features, patients with SYS are characterized by a wide phenotypic spectrum, including a variable degree of intellectual disability, language development, and motor milestones. Our results indicate that the variation in phenotypic severity may depend on the specific location of the truncating mutation, suggestive of a genotype–phenotype association. This evidence may be useful in both prenatal and pediatric genetic counseling.

Original languageEnglish (US)
Pages (from-to)2564-2574
Number of pages11
JournalAmerican Journal of Medical Genetics, Part A
Issue number12
StatePublished - Dec 2018


  • MAGEL2
  • Schaaf-Yang syndrome
  • autism spectrum disorder
  • genotype–phenotype association
  • neurodevelopment

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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