Hoarding is a form of mental illness, but it's not clear just what it is related to. Most mental health professionals believe it is a form of obsessive-compulsive disorder, although it doesn't respond to the same drugs. Some believe it may be related to Attention Deficit Hyperactivity Disorder. It's been used as a basis for several reality TV shows. I've never watched them, although I've watched American Pickers, which is a variation, and never mentions mental illness. The properties Mike and Frank visit to pick through to buy items for resale look like they're owned by hoarders.
The most famous hoarder story is probably that of Homer and Langley Collyer, who died in 1947 amidst 130 tons of trash in their decaying old brownstone in Harlem. Homer, the older of the two, had gone blind and was cared for by Langley, who had some bizarre ideas. Langley thought he could restore his brother's sight by feeding him dozens of oranges a week. Langley went out at night scrounging for food and trash to bring back to the house. He stockpiled newspapers, because he was sure when Homer's sight came back he'd want to catch up on all that had happened since he went blind.
The urban legend in New York at the time had the brothers sitting on stockpiled wealth in their house. Harlem had become African-American, and it's implied in the articles I've read that the brothers were probably fearful in their neighborhood. They had many break-ins and Langley booby-trapped the place. In the April 7, 1947 Life magazine article below, at the time of publication Langley's body had not yet been found. It was found under one of his own booby traps on April 8, 1947, partially eaten by rats. After Langley died Homer died of starvation, dehydration and cardiac arrest. It was a freak show at the time, and has lived on in various forms ever since. It's a horror story of the ultimate price of hoarding.
The comic book version is from The Big Book Of Weirdos, published in 1995 by Paradox Press, written by Carl Posey, drawn by Graham Manley, and edited by horror-humorist Gahan Wilson.