Samuel Clemens to blame for Tombstone star’s “vanishing” act, says Val.

Vanishing Val Kilmer has sparked alarm after shocking new photos emerged, depicting the former Hollywood stud as skeletal and sickly.

Back in 2013, the “Top Gun” star appeared bloated and overweight – a condition he told The National ENQUIRER was because of the long, sedentary hours he had logged toiling over a screenplay about writer Mark Twain.

Val, now 55, is proud of his redefined physique and has credited “eating right and exercising [with] long walks on the beach by my home.”

But according to top weight loss expert and diet guru, Dr. Sue Decotiis, who has not treated Val, the former “Tombstone” star is wasting away and there could be something even more sinister behind his sudden and frightening weight decline.

“Oh my God! This is crazy!” the anti-aging expert said.

“When somebody loses that much weight, you have to ask, ‘What the heck is going on?’” Dr. Decotiis said. “If he walked into my office, I’d wonder if he has some kind of serious underlying 
medical problem.

“Maybe an adrenal or thyroid problem, maybe even a pancreatic issue or – and I don’t want to sound alarmist – sometimes people look like this when they have something worse.”

Responding to fans’ fears, Val posted on Facebook: “I’m preparing as most of you know, for my dream role, Mark Twain, in a film I’ve written and will direct about his obsession with Mary Baker Eddy.

“Mark Twain was a thin man, and finally after the usual amount of effort, I’m thin again too.”

But Kilmer’s calm reassurances were not convincing to the still concerned Dr. Decotiis: “If he walked into my room, I’d be doing all sorts of tests!”