'Today, my mother forgot who I am. I feel like she just died.'

A US man sits across the table from his mother at a shopping centre food hall, sipping coffee, sharing ice cream.

“When I was sending a birthday card, which Joey was it going to? I don’t even know if I knew you,” she says. “But that doesn’t seem right, does it?”

“Don’t I look familiar?” he asks, blinking back tears.

She pauses, studying his face. “I don’t know… I think so.”

That man is Joey Daley. A 46-year-old man from Dublin, Ohio, who is documenting his mother’s experience of Lewy Body Disease, a cruel yet sadly common condition in which nerve cells in the brain deteriorate and die, causing symptoms similar to Alzheimer’s Disease.

Molly, 66, was diagnosed a year ago and has been staying in an assisted living facility ever since.

The heartbreaking weekly series, which Joey is sharing via YouTube, captures crippling decline of Molly’s memory. How she can recall her childhood, but not giving birth to her children; she can identify people in her photographs, but not how she knows them.

By episode six, shared online earlier this month, she no longer recognises her own son.

Joey. It's a name she knows, but a face she's forgotten. She talks about him, as if he's not sitting directly across from her. She rubs his arm and tell him how much she loves him, but minutes earlier couldn't recall how they met.

Joey tries to hide his devastation, but she sees it.

"Tell me what you're crying about?" she says. "I can't go to bed if you're crying."

He lies. "It's no big deal. It's just work stuff."

Later, alone in his car having dropped her home, he finally allows himself to break down.

"Hardest day of my life. When your mother doesn't know who you are. She knows my name, but doesn't know who I am," he sobs. "I tried to hard to get her to tell me who I was with photos, but she just doesn't know. I feel like she just died.

"I wasn't expecting this when I woke up this morning at all. I thought this would come a lot later, when she couldn't talk. I don't know who she thinks I am - a friend, someone she went to school with?

"I just want to go back in and ask her one more time, 'Who am I. And have her say, 'My son.'"

The full episode. Post continues after video.

The emotionally charged episode has been viewed more than 1.4 million times, and attracted thousands of comments expressing support for Joey and gratitude for his willingness to share something so personal.

For him, it's an obvious choice. One which helps shine a spotlight on a common yet little discussed disease.

"I'm doing this for my mother, the people suffering from dementia, the people that have died from dementia, the caregivers. I think the world deserves to know what those people went through," he says in the next episode.

"I just hope to make a difference."

For more information on Lewy Body Disease, visit Alzheimer's Australia website here.