RBP4 and acne: Pathogenic variants in RBP4 gene lead to reduced plasma RBP4 and all-trans-retinol concentrations and are associated with night blindness [34,169,170,171], microphthalmia [171,172], anophthalmia [172], coloboma [34,170,172], retinal dystrophy [34,169,170,171,173] and acne vulgaris [34,170,173].