PGAP1 and Brain atrophy: Also, at least three splicing defective variants of PGAP1 (MIM 611655) have been reported in autosomal recessive mental retardation‐42 (MRT42, MIM 615802) and related syndromes with psychomotor retardation and brain atrophy as well as other features (Granzow et al., 2015; Kettwig et al., 2016; Novarino et al., 2014).