An initial workup revealed non-regenerative anemia with a Hb 107 g/l and severe kidney failure with a creatinine of 756 μmol/l (8.55 mg/dl) and cystatin-C of 4.29 mg/l, corresponding to an eGFR of 7 ml/min/1.73 m2 according to CKiD-U25-creatinine. Here, GSTM1 is linked to anemia (phenotype).