Down syndrome is named after John Langdon Down, a British physician who published the first clinical description of the condition in 1866. He didn’t discover its cause or develop a treatment. He simply observed and documented a distinct pattern of physical features in patients at the institution where he worked, and his name stuck.
Who Was John Langdon Down?
In 1858, Down took a position as medical superintendent at the Royal Earlswood Asylum for Idiots in Redhill, England, one of the most prominent institutions for people with intellectual disabilities at the time. The facility had been criticized by government inspectors, and Down helped restore its reputation through better administration and patient care. He worked there for ten years while also serving as an assistant physician at the London Hospital.
Influenced by the anthropological research popular in his era, Down began systematically measuring and documenting the physical features of his young patients. He measured head diameters and described facial characteristics, attempting to classify different types of intellectual disability using the racial categories common in 19th-century science. In 1866, he published his findings in an article in the London Hospital Reports titled “Ethnic Classifications of Idiots.” In it, he described what he called a “Mongolian type,” noting a round face with angled eyes, a flat back of the head, short bristly hair, thin eyebrows, a small pug nose, and a thick tongue. A later book published in 1887 expanded on this description in greater detail.
Why “Mongolism” Was Dropped
For nearly a century, the condition was commonly called “Mongolism” or “Mongolian idiocy,” based on Down’s original racial framing. He had described his patients’ features as resembling people of Mongolian descent, a comparison rooted in a now-discredited theory that intellectual disability represented a regression to “earlier” racial types. The terminology was both scientifically wrong and deeply offensive.
In 1965, the World Health Organization recommended replacing “Mongolism” with “Down syndrome” because of the misleading racial connotation. The new name preserved credit for the physician who first characterized the condition while stripping away the racist framework he had used to describe it.
Why “Syndrome” and Not “Disease”
In medicine, a syndrome is a recognizable pattern of symptoms and physical features that tend to occur together, while a disease typically has a clearly identified cause and a well-understood progression. When Down first described the condition, no one knew what caused it. Even after the genetic basis was discovered, the term “syndrome” remained because the condition produces a wide and variable collection of features rather than a single predictable disease course. Two people with Down syndrome can have very different health profiles, different degrees of intellectual disability, and different combinations of associated conditions like heart defects or digestive problems.
The Genetic Cause Came Nearly a Century Later
Down described the outward features in 1866, but the underlying cause remained a mystery for 93 years. In 1959, French geneticist Jérôme Lejeune and his colleagues discovered that people with the condition have three copies of chromosome 21 instead of the usual two. This is why the condition is also called trisomy 21 (“tri” meaning three, “somy” referring to a chromosome body). Every cell in the body carries this extra genetic material, which alters development from very early on.
About 5,700 babies are born with Down syndrome in the United States each year, roughly 1 in every 640 births.
“Down Syndrome” vs. “Down’s Syndrome”
You’ll see both spellings, and many dictionaries list both as acceptable. In the United States, the preferred form is “Down syndrome” without the apostrophe. The National Down Syndrome Society and the AP Stylebook both recommend this spelling. The reasoning is straightforward: the possessive “Down’s” implies that the physician owned or had the condition, which he did not. He characterized it. Dropping the apostrophe keeps the name as a simple descriptor rather than a possessive. In the UK and some other countries, “Down’s syndrome” remains common, but the trend internationally has shifted toward the non-possessive form.
Advocacy organizations also recommend saying “a person with Down syndrome” rather than “a Down syndrome person” or “a Down’s child,” keeping the person’s identity separate from the diagnosis.