Pycnodysostosis
(Pyknodysostosis)

Pycnodysostosis is perhaps best known as the diagnosis given retrospectively to the late 19th century French artist Henri de Toulouse-Lautrec (portrayed by Jose Ferrer in the 1952 film "Moulin Rouge").

Pycnodysostosis is a genetic (inherited) disease of the bone. Its pattern of inheritance follows the classic rules of genetics (see below).

Pycnodysostosis consistently causes short stature. The height of adult males with the disease is less than 150 cm (59 inches, or 4 feet 1 inch). Adult females with pycnodysostosis are even shorter.

Pycnodysostosis causes the bones to be abnormally dense (osteosclerosis); the last bones of the fingers (the distal phalanges) to be unusually short; and delays the normal closure of the connections (sutures) of the skull bones in infancy, so that the "soft spot" (the fontanel) on top of the head remains widely open.

Pycnodysostosis causes brittle bones which easily break (fracture). The bones in the legs and feet tend to fracture. The jaw and collar bone (clavicles) are also particularly prone to fractures.

The precise frequency of pycnodysostosis has never been determined. Pycnodysostosis can be classified in the large group of genetic diseases that are individually uncommon, but collectively important because of the sum of their numbers, their heavy impact upon affected individuals, and the equally heavy burden they place upon their families.

The name for this disease was coined by the French physicians Maroteaux and Lamy in 1962. They described the disorder in a report entitled "La pycnodysostose." (They were not the only discoverers of the disease. Andren and colleagues independently described the condition in 1962.) Maroteaux and Lamy put "pyknos," from the Greek meaning "dense" together with the compound word "dysostosis" meaning abnormal bone formation. The name "pycnodysostosis" was designed to convey the abnormally dense bone that is a hallmark of the disease.

Although the original Maroteaux and Lamy spelling was with a 'c', it has been written variably with a 'c' or a 'k'. Here we use the original spelling with a 'c'. No matter which way it is spelt, the name has stuck and is utilized worldwide today to designate this disease.

Source: MedicineNet.com
http://www.medicinenet.com/pycnodysostosis/article.htm