RBP4 and night blindness: Vision. Two mutations p.I59N and p.G93D, corresponding to I41N and G75D of RBP4 after cleavage of the signal peptide of the mature protein, were associated with night blindness and modest retinal dystrophy without apparent effects on growth in compound heterozygous sisters (Biesalski et al., 1999; Seeliger et al., 1999).