On the frigid evening of Feb. 15, 2001, a silver-haired woman who stood less than 5 feet tall packed some skirts, blouses and underwear into two brown shopping bags. She put on her gray winter coat, locked the door to her Skokie home and fled. After she wandered the dark and empty streets of the northern suburb for a couple of hours, the police picked her up and deposited her at a nearby relative's home. The next morning she was out the door and running again, only to be grabbed by the Skokie police once more.

Someone was trying to kill her, "to put a bullet in my head," the 69-year-old woman told anyone who would listen. But no one in the emergency room of Rush North Shore Medical Center, where the police brought her, nor in the hospital's locked-down psychiatric ward, where she was placed a few hours later, believed this claim, or any of the others she made.They couldn't imagine that someone had painted yellow Stars of David on her front lawn, or that the food she was being served in the hospital was covered with lice or that each night voices told her she was going to be killed and, therefore, she had to run.

To her, these delusions were as real as life itself. Her psychotic visions revived a nightmarish past in which she, as an 11-year-old girl, escaped the Jewish ghetto in Dubno, Poland, as her family and friends were being shot by German death squads.

Although no one knew it, she was suffering from a little-known mental illness that only recently had been diagnosed among aging Holocaust survivors.

The woman--my mother, Sonia Reich--hardly had spoken of the horrors she experienced, though occasionally she had mentioned that, as a child, she was "running and running, I didn't know where I was running." She described sleeping on the ground and working on farms for scraps of food. She was filthy and ridden with lice. She told my sister, Barbara, that she was "in fields alone and people were shooting at me."

But that was nearly all she revealed about this harrowing period of her life.

Almost 60 years later, a widow who had led a stable postwar existence--raising a family and taking trips to California to visit her grandchildren--suddenly and inexplicably began re-enacting her past.

When the police first brought my mother to the hospital, the emergency-room doctors gave her a full run of neurological exams, including brain scans, which showed no abnormalities. Her personal physicians could find no explanation for what was happening to her.

Eventually, I learned what was wrong from several specialists I contacted around the world: My mother had late-onset post-traumatic stress disorder.

PTSD did not enter the psychiatric lexicon until 1980, and the delayed form that my mother had remains unknown to many physicians.

After spending decades coping with frightening memories, many late-onset patients finally begin losing the war against their pasts. Catastrophic events that they experienced long ago reinsert themselves into their lives, the strands of the past and the present becoming inextricably bound, with medicine virtually incapable of unraveling them.

No one knows how many people have this form of the disorder, largely because some disappear into the nursing-home population or their symptoms are mistaken as Alzheimer's disease or other age-related mental illness.

"Your mother has late-onset PTSD with bells and whistles," said Dr. David Rosenberg, a Highland Park psychiatrist who has been evaluating Holocaust survivors for more than 40 years.

Last year, he was hired by the German Consulate General in Chicago to assess whether my mother qualified for a small increase in the monthly reparations payments she had been receiving since the late 1960s.

But money was not going to change her condition, so I decided not to pursue it.

"To see someone like her, to be able to do nothing to help and then to wash your hands of it is very difficult," Rosenberg said.

"You feel helpless. You feel almost as helpless as she is."

There was nothing any doctor could do to pull my mother from a thicket of paranoia and delusion. She refused to talk to doctors or nurses. She said they were trying to poison her, which was why she would not take any of the powerful drugs that fight psychosis.

She fervently denied, as many such patients do, that anything was wrong with her, focusing her energies on eluding the killers she believed were hunting her.