That is, we previously investigated the effects of anemia correction with recombinant human erythropoietin on cerebral blood flow and oxygen metabolism in HD patients, and showed that regional cerebral metabolic rate for oxygen (rCMRO2) significantly increased in the frontal cerebral cortex, but not in the other cerebral cortices, deep gray matter, white matter, and cerebellum, after the correction of anemia [33]. The gene discussed is EPO; the disease is anemia (phenotype).