NSD1 and Global developmental delay: NSD1 gene mutations cause Sotos syndrome (OMIM 117550), a rare autosomal dominant disorder characterized by four main features: (1) dysmorphic facial features (e.g., macrocephaly, prominent forehead, high hairline, downslanting palpebral fissures, long narrow face, pointed chin, sparse frontotemporal hair); (2) overgrowth (prenatal and postnatal accelerated growth, height and/or head circumference ≥2 SD); (3) advanced bone age; and (4) developmental delay (learning difficulties, mild to severe intellectual disability) (Luo, 2020).