He was once the mischievous, cherubic star of the hugely successful Home Alone movies.
However, Macaulay Culkin, now 31, appeared dishevelled and emaciated as he greeted fans in New York on Wednesday.
With his straggly goatee beard and messy hair, he looked gaunt as he sipped from an energy drink.
Tonight, something just came up and he couldn't make it.'
But his spokesperson insists there is no need for concern, saying in a statement: 'Macaulay Culkin is in perfectly good health.'
His appearance was a far cry from the cute youngster who shot to international fame playing cheeky Kevin McCallister in the 1990 family favourite.
Culkin was once Hollywood’s biggest child star, commanding £4million a film by the time he starred in 1994’s Richie Rich.
But the young actor soon hit troubled times and has weathered a number of personal tragedies, including the death of his sister Dakota in a car crash and of his half-sister Jennifer Adamson from a drug overdose.
His career then came to a halt after he was embroiled in a messy financial dispute between his parents Christopher Culkin and Patricia Brentup.
In 1998 a judge fired his father - who was his manager - and handed control of his vast personal fortune to an accountant until he turned 18.
After a hiatus, he returned to films in 2000.
However, none of his subsequent movies have come near to matching the success of the Home Alone series.
Culkin dated Mila Kunis , pictured here in 2005, for eight years before they split in 2010
He took the stand and vehemently denied any inappropriate behavior or touching during the times he slept at Jackson's Neverland Ranch.
He was amoung the mourners at the King of Pop's funeral at Forest Lawn Memorial Park in Glendale, California, in September 2009.
Culkin is rumored to be starring in the upcoming British military film Service Man, which is set for release next year.