This is any one of a group of rapidly progressive degenerative neurological diseases that include Scrapie in sheep, Bovine Spongiform Encephalopathy (BSE) in cattle and “Kuru” and “Creutzfeldt Jacob Disease” in humans.
In humans the Spongiform Encephalopathy are characterized by rapidly progressive dementia associated with a sudden spasm of the muscles, known as myoclonic jerks (myoclonus), which tends to occur on falling asleep.
On pathological examination the brains of affected individuals show a characteristic cystic degeneration. The diseases are thought to be caused by unconventional transmissible agents.
A prion is an abnormal form of a constituent protein (PrP) of brain cells. Prions are produced by mutations in the gene that codes for PrP and are very stable : they are not removed by the normal cellular processes of degradation and are resistant to radiation. They are believed to interact with normal PrP in such a way as to convert it to the abnormal form, which accumulates in the brain.
Prions are now widely accepted as being the causal agents of a range of serious diseases including Creutzfeldt Jacob Disease, Gerstmann Straussler
syndrome, and Kuru, all of which are spongiform encephalopathies. Different
mutations in the PrP gene are believed to be responsible for the different forms of
these so-called prion diseases.
CREUTZFELDT DISEASE (CJD)
This is a rapidly progressive rare neurological disease, a form of spongiform encephhalopathy in which dementia progresses to death after a period of 3-12 months.
There is no effective conventional western treatment. The causative agent is currently believed to be an abnormal prion protein that accumulates in the brain and causes wide-spread destruction of tissue.
CJD typically affects middle-aged to elderly people.
Some 15% of cases are due to a form of the disease that is inherited as an autosomal dominant characteristic but most cases are sporadic, susceptibility being genetically determined.
A few cases are acquired : the agent is known to have been transmitted by tissue and organ transplantation and by human growth hormone injections, but the disease may take years to manifest itself.
Bovine Spongiform Encephalopathy (contd.)
A new variant form of acquired CJD affecting younger people has been linked with the consumption of meat products containing tissue from cattle infected with bovine spongiform encephalopathy (BSE); however no causative effect has yet been established.
It was discovered by two German psychiatrists, H.G. Creutsfeldt (1885-1964) and A.M. Jakob (1884-1931)
GERSTMANN STRAUSSLER SYNDROME
This is characterized by a group of symptoms that represent a partial disintegration of the patient’s recognition of his body image. It consists of an inability to name the individual fingers, a misidentification of the right and left sides of the body, an inability to write or make mathematical calculations.
It is caused by disease in the association area of the left parietal lobe of the brain.
It was discovered by the U.S. neurologist, J.G. Gerstmann (1888-1969).
This is a disease that affects only members of the Fore tribe of New Guinea. It involves a progressive degeneration of the nerve cells of the central nervous system, particularly in the region of the brain that controls movement. Muscular control becomes defective and shiver-like tremors occur in the trunk, limbs and head.
Kuru affects mainly women and children and usually proves fatal within 9-12 months.
It is thought to be caused by a prion and transmitted by cannibalism.
Extracted from the 1998 Oxford Concise Medical Dictionary,
Published by the Oxford University Press,
Great Clarendon Street, Oxford OX2 6DP, U.K.