PrP systemic amyloidosis is an extremely rare and unusual form of inherited prion disease. Unlike most prion diseases, PrP systemic amyloidosis is not isolated to the central nervous system. The prion amyloid has extensive peripheral involvement, finding its way to peripheral nerves and internal organs. The initial presentation of this disease involves chronic diarrhea and autonomic neuropathy before progressing into neurodegeneration.
Symptoms.
The initial presentation of PrP systemic amyloidosis is chronic diarrhea in the fourth decade of life, which may be misdiagnosed as Crohn's disease or irritable bowel syndrome. Sensory and/or autonomic neuropathy follows. 
In one case, the disease caused optic nerve atrophy and visual disturbances in a Japanese woman.
Eventually, the disease will impact the central nervous system, leading to cognitive decline, seizures, and death.
Causes.
PrP systemic amyloidosis is caused by a genetic truncation of PRNP.
There is concern of potential iatrogenic transmission, as bowel symptoms may be investigated or treated through surgical means. However, mouse studies did not show transmissibility.