When Lucy Hoggan’s son Cadell laughs, the sound literally fills her with dread.

Cadell, 3, has a rare form of gelastic epilepsy, which causes strange bouts of laughter – and could one day kill him, London’s Daily Mail reported Monday.

“Cadell may sound like he’s laughing, but his eyes are filled with fear,” said Hoggan, 38, of Aldershot, Hertfordshire, England. “He’s laughing, but his eyes are panic stricken.”

Hoggan said the fits of laughter happen about 10 times a day and usually at inappropriate times.

“One minute he’ll be serious or relaxed, the next he’ll be manically laughing,” she said. “Afterwards, he cries or wants a cuddle and some reassurance.”

Children with gelastic epilepsy can suffer more than 200 acute seizures a day; leaving them so exhausted they pass out and/or stop breathing.

The epilepsy is caused by a benign tumor called hypothalamic hamartoma, which is located in the center of his brain. Doctors told Hoggan that Cadell will eventually need the tumor removed, as the severe laughing fits could literally end his life.

However, surgical removal of the tumor is risky and difficult, according to epilepsy.com. Medical treatment is often ineffective.

Click here to read the full story from the Daily Mail and to see pictures of Cadell.

Click here to learn more about gelastic epilepsy.