Other important MRPs include ABCC2 (MRP2), crucial for biliary excretion of organic anions and associated with Dubin–Johnson syndrome [48]; ABCC3 (MRP3), which transports bile acids and conjugated bilirubin from the liver to the blood [49]; ABCC4 (MRP4) and ABCC5 (MRP5), which mediate the efflux of cyclic nucleotides and antiviral drugs [50]; and ABCC6 (MRP6), associated with pseudoxanthoma elasticum [51]. This evidence concerns the gene ABCC4 and pseudoxanthoma elasticum (inherited or acquired).