A little Irish boy from Kerry who underwent pioneering surgery in New York has lost his brave battle with Battens Disease.

Liam Heffernan passed away on Sunday morning, four years after the disease claimed the life of his sister Saoirse, who died at the same age in 2010.

Dad Tony tweeted the news from the hospital on Sunday morning when he wrote: "#LittleLiamo has grown angelwings & joined sister Saoirse in heaven #RIP son #SuperHero No More #BattenDisease".

Tony had posted a heartbreaking photo on Twitter last Monday of his son in the emergency room.

He revealed then that the five-year-old’s condition was ‘very very poorly.’

Liam had traveled from Kerry to New York in 2011 for life saving surgery at Weill Cornell University.

His parents Tony and Mary had opted for his gene transfer surgery in New York as part of a medical treatment trial.

He underwent the surgery just a year after the death of his sister Saoirse from the disease.

The Irish Independent website reports that last year Liam lost his sight and began suffering a surge in seizures.

Tony and Mary Heffernan were told then that their son would more than likely pass away in 2014.

Over the past 2 months Liam went blind, lost nearly all mobility and was not able to consume solid foods.

Dad Tony said at the time: “It’s not easy, there are no resources. At the moment, we don’t get much assistance.

“You keep asking and asking, and hoping something will happen, but that’s life. His lifespan is less than 12 months to live, apparently. His sister died at five and a half and he turned five on July 3rd.”

Tony and Mary Heffernan campaign to raise awareness about the rare condition that is Batten’s disease and run the Saoirse Foundation, supporting other Irish families in similar positions.

Bees for Battens is an online campaign for raising awareness and supporting those affected by Battens disease.

More details are available at www.beeforbattens.orgs.