Owing to its essential role in erythropoiesis, changes inhuman ALAS2 (hALAS2) function can lead to two different blood disorders.X-linked sideroblastic anemia results from loss of ALAS2 function,while X-linked protoporphyria results from gain of ALAS2 function.Interestingly, mutations in the ALAS2 C-terminal extension can beimplicated in both diseases. This evidence concerns the gene ALAS2 and X-linked sideroblastic anemia 1.