Walking corpse syndrome – cotard delusion. 17 years in mental health and I’ve seen it once.
The belief that some or all of you is dead.
The guy was so certain he was dead he believed he was a zombie.
Fetus-in-fetu. 10 year old boy "pregnant" with his parasitic twin (PT).
10 y.o. boy came in with enlarging abdominal mass and intermittent generalized weakness. Imaging revealed a parasitic "fetus" which was also growing in size. History revealed mass noted 2 years ago which enlarged rapidly the last 3-4 months. Within days of admission, boy's organs begin to fail with no apparent reason. He was healthy and eating well when he was admitted. Family wanted surgical intervention to separate the parasitic twin against surgeons' advice. parasitic twin was basically starving/poisoning the boy to death. Surgeons opened the boy up and found that the boy and parasitic twin share a (stomach, liver, heart, blood vessels – mesodermal organs) basically too complex to operate. The boy passed away after.
This happened to a poor family in a underfunded government hospital in a corruption-infested country. The parasitic twin was donated to the hospital. It had teeth with hairy limbs with the longest curved baby nails. I can't describe it further. It is on display at the Surgeon's Hall.
Edit 2:This happened years ago before the age of smartphones.The hospital team tried to have the tissues studied for academic purposes. there was a case report about it presented in a local medical congress but as this happened in a "third world" country with limited resources, nothing came of it. I live and work in a different country now.
Last Edit: NSFW if you want to google it.