A blood disorder which is caused by a genetically determined change in the molecular structure of hemoglobin: Hemoglobinopathy is an ailment due to abnormalities in the hemoglobin molecule, the best known being "sickle cell anemia" in which there is a single amino acid substitution ("valine" for "glutamate") in position six of the beta chain. In other cases one of the globin chains is synthesised at a slower rate, despite being normal in structure.