As SCD is responsible for intravascular hemolysis, SCD patients have lower concentrations of haptoglobin (0.09 versus 1.18 g/L, p < 0.0001) and hemopexin (0.42 versus 1.05 g/L, p = 0.0001) than unaffected controls [AG Cordier and K Peoc’h, Personal communication]. This evidence concerns the gene HPX and Schnyder corneal dystrophy.