Čes-slov Pediat 2025, 80(90):18-21 | DOI: 10.55095/CSPediatrie2025/047

Schaaf-Yang syndrome - a rare cause of hypopituitarism and central diabetes insipidus

Renata Pomahačová¹, Petra Paterová¹, Eva Nykodýmová¹, Petr Polák¹, Josef Sýkora¹, Ivan Šubrt², Radka Jaklová²

¹ Dětská klinika, Lékařská fakulta a Fakultní nemocnice v Plzni, Univerzita Karlova, Plzeň

² Ústav lékařské genetiky, Lékařská fakulta a Fakultní nemocnice v Plzni, Univerzita Karlova, Plzeň

Schaaf-Yang syndrome (SYS) is a rare autosomal dominantly inherited disorder caused by pathogenic sequence variants of the MAGEL2 gene. The gene is subject to genomic imprinting with expression of only

the mutated paternal allele of the MAGEL2 gene. SYS shares many clinical features with the genetically related Prader-Willi syndrome (PWS), which is related to the localization of the gene in the PWS-like region on chromosome 15. SYS is characterized by a variable phenotype with facial dysmorphism, joint contractures, muscle hypotonia, respiratory problems, eye defects, psychomotor retardation

(PMR), endocrine disorders, failure to thrive in the neonatal/infantile period and, conversely, obesity in later life. In PWS, the dominant symptoms are obesity and hyperphagia, while in SYS, autism spectrum disorder and joint contractures are the opposite. Common symptoms in PWS and SYS are muscle hypotonia, feeding disorder after birth, PMR and male hypogonadism with clinical signs of

hypogenitalism after birth. We describe our own experience and the latest findings on SYS with a focus on possible endocrine disorders and the effect of growth hormone treatment in these patients.

Keywords: Schaaf-Yang syndrome, Prader-Willi syndrome, MAGEL2 gene, joint contractures, hypopituitarism, central diabetes insipidus, growth hormone

Accepted: September 23, 2025; Published: September 1, 2025  Show citation