The elderly woman is suspected of pulling her son out of school when he was 12 years old and keeping him indoors ever since.
ADVERTISEMENTA 70-year-old woman has been arrested on suspicion of locking her son inside their apartment for 28 years in eastern Stockholm in Sweden.
The man, who is 41 years old, is reported as being undernourished and with almost no teeth.
He was discovered while his mother was in hospital last month after a relative managed to get into the flat. There she found the man lying on the floor covered in sores.
According to reports, the woman pulled her son out of school when he was 12 years old and kept him inside ever since.
"The mother is suspected of illegal deprivation of liberty and causing bodily harm," said Stockholm police spokesman Ola Osterling.
"The man is in hospital. His injuries are not life-threatening," added Osterling.
The Swedish Prosecution Authority has said the elderly woman has denied the crimes.
The apartment block is in a suburb of Handen in Haninge municipality. Police have tape stretched across the flat's door after crime scene technicians left the scene.
It's reported that the relative said the home looked like it hadn't been cleaned in years.
The family member, wishing to stay anonymous said, "I'm in shock, brokenhearted, but at the same time relieved. I've been waiting for this day for 20 years because I figured out that she was totally controlling his life, but I never imagined the extent of it."
"I knew he was there and that he must be scared because his mother was his only sense of security and now she was gone," she added.
According to local media, one unidentified neighbour said that she ran into the man at a nearby grocery store a few months ago.
"I know who you are, you're my neighbour," the man had told her, recognising her after having seen her through the window, she said.
Other neighbours told journalists they hadn't seen the man for a long time and wondered why social services or the school didn't check in on the boy when he didn't go to class all those years ago.