The 55-year-old woman, identified as Laura Carla Lodola, was discovered in the apartment in Pavia, northern Italy, on Monday morning after her partner, Antonio Calandrini, alerted emergency services when she fell unconscious, Tgcom24 reported.
She was taken to hospital but died on Wednesday morning, Il Mattino reported.
Calandrini was arrested on Monday and accused of neglecting a person of unsound mind.
When the ambulance crew arrived at the scene they were confronted with a horrifying spectacle.
The skeletal woman, who was covered in bedsores and had long hair and finger nails, had been living in filthy conditions. Doctors suspect she had been bedridden for years.
“She looked like a small shrunken mummy,” a health worker was quoted as saying.
Police must now determine whether Calandrini forced Lodola to live in such conditions.
Last year, a 36-year-old woman was found among piles of rubbish in an apartment in Naples after allegedly being held captive there by her mother for eight years.
The woman was found “curled up behind a sofa, semi-naked and trying to warm herself with a hair-dryer” and in a poor “physical and mental state”, according to a report in Il Messaggero.