Among patients with severe TBI and prolonged hospitalization, a late decrease in the Hb level is likely to resemble the anemia seen in the general critical care population during an extended LOS in the ICU, involving hemodilution, repeated phlebotomies, and inflammatory processes resulting in bone marrow suppression and impaired erythropoiesis [30]. The gene discussed is GSTM1; the disease is anemia (phenotype).