MBD5 and Marchiafava-Bignami disease: 2010). Patients with intragenic MBD5 rearrangements and frameshift mutations of MBD5 are phenotypically indistinguishable from those with 2q23.1 deletions (Kleefstra et al. 2012; Carvill et al. 2013; Camarena et al. 2014; Bonnet et al. 2013). The deletion is highly penetrant and is associated with a broad phenotypic spectrum (MBD‐Associated Neurodevelopmental Disorders) (Mullegama and Elsea 2016; Camarena et al. 2014).