The GRBGD-associated LBR mutations p.N547D and p.R583Q substitute amino acids highly conserved in homologous C14 sterol reductases and have recently been shown to selectively abrogate the binding capacity of the enzymatic core for reduced nicotinamide adenine dinucleotide phosphate (NADPH), a cofactor absolutely required for the reduction of sterol substrates by LBR (12). Here, LBR is linked to Greenberg dysplasia.