Three patients with Schaaf-Yang syndrome exhibiting arthrogryposis and endocrinological abnormalities.

MAGEL2 is the paternally expressed gene within Prader-Willi syndrome critical region at 15q11.2. We encountered three individuals in whom truncating mutations of MAGEL2 were identified. Patients 1 and 2, siblings born to healthy, non-consanguineous Japanese parents, showed generalized hypotonia, lethargy, severe respiratory difficulty, poor feeding, and multiple anomalies including arthrogryposis soon after birth. We carried out whole-exome sequencing, which detected a MAGEL2 mutation (c.1912C>T, p.Gln638*, heterozygous). The patients' father was heterozygous for the mutation. Patient 3 was a female infant, showed respiratory difficulty reflecting pulmonary hypoplasia, generalized hypotonia, feeding difficulty and multiple anomalies soon after birth. Targeted next-generation sequencing detected a novel heterozygous mutation in MAGEL2 (c.3131C>A, p.Ser1044*). This mutation was not found in the parents. MAGEL2 mutations, first reported to be the cause of the Prader-Willi like syndrome with autism by Schaaf et al. (2013) Nature Genetics, 45: 1405-1408 show the wide range of phenotypic spectrum from lethal arthrogryposis multiplex congenital to autism spectrum disorder (ASD) and mild intellectual disability (ID). Our results indicate that MAGEL2 mutations cause multiple congenital anomalies and intellectual disability accompanied by arthrogryposis multiplex congenita and various endocrinologic abnormalities, supporting that the view that clinical phenotypes of MAGEL2 mutations are variable.