health

CJD is thought to be caused by a prion, an infectious protein particle that
causes similar normally folded protein molecules in the brain to refold
themselves into abnormal shapes. The misfolded proteins accumulate in
the brain tissue, interfere with the functioning of the brain cells, and eventually
cause the death of the brain tissue. Classic CJD is thought to have an
incubation period as long as twenty to forty years.

A person can develop CJD in one of three ways:

• Sporadic. Sporadic means that the disease appears at random for
  no apparent reason. About 85 percent of cases of CJD are
  sporadic.
  
• Genetic. A gene mutation in some families accounts for 5–10 percent
  of cases of CJD.
• Acquired. CJD can be acquired through blood transfusions or
  transplantation of tissues taken from a person with CJD. This is
  the rarest form of CJD, accounting for about 1 percent of known
  cases. It is important to know, however, that people cannot get
  acquired CJD through the air or from casual contact with a CJD
  patient. It is exposure to brain or spinal cord tissue or spinal fluid
  from an infected person that puts others at risk.

The chief difference between classic CJD and variant CJD is the age
group affected. Most persons with classic CJD are middle-aged or older
adults, whereas the average age of persons with variant CJD is twentyeight
years. It is also thought that variant CJD may have a shorter incubation
period than classic CJD, perhaps only eleven or twelve years in
length.

The symptoms of CJD include psychiatric as well as physical
symptoms:

• Anxiety and nervousness
  
• Difficulty walking normally; stumbling and falling
  
• Loss of coordination and spontaneous muscle twitching
  
• Seizures
  
• Visual problems and eventual blindness
  
• Mental confusion and personality changes
  
• Rapidly developing delirium and dementia
  
• Difficulty talking normally
  
• Hallucinations