Ten patients were diagnosed based on additional specific genetic tests; congenital myotonic dystrophy with a mutation in DMPK (n = 2), spinal muscular atrophy type 2 with a mutation in SMN1 (n = 2), Prader-Willi syndrome confirmed by methylation test (n = 1), Rett syndrome with a mutation in MECP2 (n = 1), fragile X syndrome with a mutation in FMR1 (n=1), Sotos syndrome with a mutation in NSD1 (n = 1), Crouzon syndrome with a mutation in FGFR2 (n = 1), and Menkes disease with a mutation in ATP7A (n = 1). The gene discussed is NSD1; the disease is Prader-Willi syndrome.