Methemoglobinemia

Part of speech: noun

Definitions

1. A health condition resulting from elevated levels of methemoglobin in the blood that hinders the effective transport of oxygen
2. A medical disorder marked by an increased presence of methemoglobin which reduces the blood's capacity to carry oxygen
3. A disorder characterized by an abnormal amount of methemoglobin in the bloodstream, impairing oxygen delivery to tissues

Etymology: Methemoglobinemia is a compound built from three Greek-derived pieces. "Meta-" from Greek "metá" means change or after, "haima" means blood, and "-emia" comes from Greek "haima" as well, meaning a condition of the blood. The name therefore describes a blood condition in which haemoglobin has been altered into a different form. The middle element, methemoglobin, is itself a compound. Haemoglobin is the oxygen-carrying protein in red blood cells, and its iron sits in a ferrous state that can bind oxygen. When that iron is oxidised to the ferric state, the protein becomes methemoglobin, which cannot carry oxygen. The "meta" prefix thus marks a chemical change from the normal form, and "-globin" links the term to globulin proteins. The disorder itself, with the suffix "-emia" added to form a clinical condition name, follows the pattern of many medical terms built from Greek roots. Such coinages date from the late nineteenth and early twentieth centuries, when physicians were naming blood chemistry discoveries, so the word is a modern scientific creation rather than an ancient one.