They're being called the "Benjamin Button" brothers--a reference to "The Curious Case of Benjamin Button," the 2008 movie in which Brad Pitt plays a man who ages in reverse.
Matthew Clark, 39, of Lincoln, England and his brother Michael Clark, 42, last year were reportedly given a vague diagnosis of terminal leukodystrophy. The brothers' particular version of the disorder caused them to lose the ability to think and behave as adults, The Telegraph reported.
After a phase of throwing temper tantrums and watching cartoons, the brothers have gradually lost the ability to talk and walk, leaving them crawling around their parents' home, the U.K. tabloid Mirror reported.
“It’s a devastating disease," the men's father, Anthony Clark, told The Telegraph. "Both of them are very childlike now.”
Neither paper indicated which form of leukodystrophy the men have--there are about 40 known types of the largely genetic brain cell-damaging disorder--or who diagnosed the brothers.
Is it really possible for adults to revert to a childlike state? Experts in the U.S. told The Huffington Post that it is--though it occurs very rarely.
"'Leukodystrophy' is a term used for progressive disorders that causes damage or deterioration to the white matter of the brain," Dr. Robert Marion, chief of genetics and developmental medicine at Albert Einstein College of Medicine in New York City, told The Huffington Post.
Dr. Marion, who said he had no specific knowledge of the brothers, added that the disorder they reportedly have is hereditary and that the mental deterioration happens gradually.
There are infantile, juvenile and adult forms of leukodystrophy. As for cases that apparently arise in adulthood, Dr. Marion said, "It’s possible that nobody has really noticed it [until] its gotten so bad that it's reached this level of detection. They reach adulthood or later adolescence and they’ve attained everything they could, then start having neurological symptoms. They can have dementia, they start losing their memory or their ability to function...they’ll lose their ability to walk, wind up wheelchair-bound."
Dr. David Wenger of Jefferson Medical College in Pennsylvania, has diagnosed many leukodystrophy patients. He told The Huffington Post that a number of diseases could cause a deterioration of mental capability--for example, Krabbe disease, and even multiple sclerosis.
"You have to be really careful," Dr. Wenger said about diagnosing neurological diseases. "These are tough disorders to treat."
Loading comments… 
The Huffington Post | By Jacqueline Howard Posted: 05/ 2/2012 8:54 pm Updated: 05/ 3/2012 12:56 pm