Given the heterogenous presentation, HS has been classified in classified in trait (normal Hb and reticulocytes, unconjugated bilirubin < 1 mg/dL), mild (Hb > 11 g/dL, reticulocytes 3–6%, unconjugated bilirubin 1- 2 mg/dL), moderate (Hb 8–12 g/dL, reticulocytes 6–10%, unconjugated bilirubin > 2 mg/dL) and severe (Hb > 8 g/dL, reticulocytes > 10%, unconjugated bilirubin > 3 mg/dL) [9]. This evidence concerns the gene GSTM1 and histiocytic sarcoma.