Oldest progressive condition

 It has become known as the "second oldest progressive condition" after Parkinsonism where there have been almost 200000 cases reported since 1950. - The first case was described in 1943 but later diagnosed with multiple sclerosis, which eventually led to the neurodegenerative disease of central nervous system and caused many deaths by 1970. Image source: wikipedia When Alzheimer's Disease is seen on a genetic level it turns out that around 90% – probably more than 95%- comes from one specific gene (called apolipoprotein E receptor γ) although both ApoE and AD risk factors are present across different genes for some people so having two or three copies of an allele may not help very much if you suffer from only sporadic symptoms rather then severe chronic depression.  

 A diagnosis of schizophrenia is not a simple one but requires an individual to develop and express aspects that are characteristic for each patient.