Hoarding disorder usually affects older people who live alone. It is characterized by the total personal and social abandonment of a person, as well as by the voluntary isolation of that same person.
A hoarder spends most of their time at home and over time accumulates objects, rubbish and domestic waste in large quantities. A hoarder can be a danger to not only themselves, but to their neighborhood or apartment building. Accumulation attracts rodents, infections, insects, falls, or landslides due to overweight.
Sometimes this disorder is called Diogenes syndrome, but that is incorrectly named. Diogenes of Sinope was a Greek philosopher that was a huge advocate and promoter of the ideas of deprivation and independence from material goods, which is the opposite of what a hoarder is.