DISCUSSION
MAGEL2 is a paternally expressed, maternally imprinted,
protein-coding gene located on chromosome 15. MAGEL2 is one of
the genes that falls into the paternally expressed region of chromosome
15 (15q11-q13) known to result in Prader-Willi Syndrome (PWS, MIM:
#176270)8. Prader-Willi Syndrome is characterized by
hypotonia, feeding difficulties followed by hyperphagia later, failure
to thrive, developmental delay and, hypogonadism in
males.9 Schaaf-Yang Syndrome (SYS) has a great deal of
clinical overlap with PWS in that affected individuals often have
hypotonia, feeding difficulties, failure to thrive, developmental
delay/intellectual disabilities, and hypogonadism.8However, individuals with Schaaf Yang are more likely to have congenital
contractures ranging from mild to severe, autistic spectrum disorder and
hypopituitarism.10,11,12 Hyperphagia which is common
in PWS is not a common feature of SYS. Truncating mutations inMAGEL2 appear to be more consistent with classic SYS phenotype,
whereas whole gene deletions including the promoter region inMAGEL2 have been found to have milder phenotypic
consequences.13,14 This may be due to a dominant
negative effect of the truncated protein or due to ‘leaky’ expression of
the maternal copy of MAGEL2 in whole gene deletion cases which
has been suggested in mice studies 9,12.