Anemia in cardiorenal syndrome is multifactorial, and various mechanisms are implicated: the use of renin–angiotensin–aldosterone system inhibitors that leads to decreased erythropoietin synthesis; low cardiac output that is responsible for bone marrow hypoperfusion; the inflammatory status that causes erythropoietin resistance; iron deficiency, hemodilution, and gastrointestinal blood losses [5]. The gene discussed is REN; the disease is anemia (phenotype).