GDF6 and Chiari malformation type I: GDF6 A249E mutation is also linked to microphthalmia/anophthalmia with and without skeletal abnormalities (Asai-Coakwell et al., 2009; den Hollander et al., 2010; Gonzalez-Rodriguez et al., 2010; Slavotinek et al., 2015), hereditary retinal dystrophy (Asai-Coakwell et al., 2013), and Chiari type I malformation (displacement of the cerebellar tonsils below the base of the skull) (Markunas et al., 2013).