TAF1 and X-linked intellectual disability: TAF1 missense variants in males (maternally inherited or acquired de novo) can cause the neurodevelopmental disorder X-linked syndromic intellectual developmental disorder-33 (MRXS33) also known as X-linked intellectual disability (XLID), which may present with craniofacial abnormalities and a variety of other clinical features including congenital heart disease (Gudmundsson et al., 2019; O'Rawe et al., 2015).