MWS is a multiple congenital anomaly syndrome, first clinically delineated by Mowat et al in 1998. Over 45 cases have now been reported. All patients have typical dysmorphic features in association with severe intellectual disability, and nearly all have microcephaly and seizures. Congenital anomalies, including Hirschsprung disease (HSCR), congenital heart disease, hypospadias, genitourinary anomalies, agenesis of the corpus callosum, and short stature are common. The syndrome is the result of heterozygous deletions or truncating mutations of the ZFHX1B (SIP1) gene on chromosome 2q22.