GSTM1 and anemia (phenotype): However, while splenectomy leads to substantial anemia recovery in hereditary spherocytosis (HS), it is considerably less effective in PKD and CDAs, and most patients remain transfusion-dependent (median Hb increase of 3 g/dL in HS, 1.6–1.8 g/dL in PKD, and 1 g/dL in CDA type II).