Ochronose

Part of speech: noun

Definitions

1. A dark bluish-black discoloration of connective tissue caused by a buildup of homogentisic acid in people with alkaptonuria
2. The darkening of cartilage and other body tissues that results from an inherited metabolic disorder called alkaptonuria
3. A pigment change in connective tissues, turning them blue-black, that arises when the body cannot break down homogentisic acid

Etymology: Ochronosis is a medical term for a condition in which connective tissue, especially cartilage and the sclera of the eye, turns a yellowish-to-blue-black colour. The most striking part of the story is that the colour comes from the body's own chemistry: in alkaptonuria, a rare inherited disorder, the body cannot break down homogentisic acid, which builds up and oxidises into pigments that stain tissue dark. The name itself was coined in the late nineteenth century, not in antiquity. It was built from the Greek "ōchros", meaning pale yellow or ochre, and the suffix "-osis", denoting an abnormal condition, so it literally names a disease of yellowness. The yellow part of the name is the surprise, since the end result is so dark. Early clinicians noticed the yellowish stage of the tissue changes before the darkening became obvious, and the term reflects that observation. The word belongs to the same family of Greek-based medical coinages as many other nineteenth-century diagnostic terms, drawn from classical roots to describe conditions that the ancient Greeks themselves never identified.