GALK1 and Renal glucosuria: Other examples where early onset cataract is the major manifestation of an underlying systemic disorder include renal glucosuria due to solute carrier family 16, member 12 (monocarboxylic acid transporter 12; SLC16A12) mutations [19], and lactose intolerance due to galactokinase 1 (GALK1) mutations [20].