An inspirational Australian with dwarfism has died at the age of 22.

Leo Lagana was born with primordial dwarfism type II, which causes skeletal abnormalities, and was 93cm tall and weighed 20kg.

He had been in and out of hospital over the past month, as his condition deteriorated and died on Monday morning.

'I'm so sorry I couldn't do more for you ...' his heartbroken mother said on Facebook.

'RIP my angel. Mum and Dad have such a void now. Forever broken.'

Hundreds have remembered Leo for his strength and determination in tributes posted online.

'I am heartbroken at the passing of Leo,' Patricia Palombo Grasso said. 'I can only imagine the pain the family are feeling.

'Leo in one way or another has touched us all over the years. He was a strong and determined little man who brought all of joy, tears and courage. We are all blessed to have known him.'

'I am deeply saddened to hear of the passing of this brave little man Leo Lagana who has endured many health challenges in his short life,' Libby Petrella added.

Before his death, Leo's mother dedicated countless hours trying to raise awareness of his condition after he was bullied on social media and called a 'freak'. 

'People come up to me and say, "What's wrong with him?" I don't mind at all. It's better they ask, rather than standing there and staring,' she said. 

'I think the world needs to be educated.' 

Ms Lagana said she and her husband 'hit the jackpot' with Leo and they have enjoyed every day with him. 

She previously said her son 'walks down the street like he's 10ft tall' thanks to his 'loud, gregarious, cheeky and very social' personality.

The schoolboy defied doctors since he was born weighing just 1.6 kilograms and 28 centimetres long.

He suffered from aneurysms - an excessive localised swelling of the wall of an artery - and a rare form of brain disease called Moyamoya. 

Leo's condition is extremely rare - a one in 130 million chance - that only affects 200 people worldwide.