However, other factors, such as shortened RBC lifespan, EPO resistance due to local or systemic inflammation, diabetes, absolute iron deficiency, especially due to gastrointestinal bleeding or impaired absorption of iron, functional iron deficiency due to hepcidin-induced disordered iron metabolism, and reduced level of vitamin B12 or folic acid, can also contribute significantly to anemia (Hsu et al., 2002; El-Achkar et al., 2005; de Francisco et al., 2009; Yilmaz et al., 2011; Babitt and Lin, 2012; Koury and Haase, 2015). The gene discussed is EPO; the disease is anemia.