| Last updated
The family from Bristol - who wish to remain anonymous - said they first knew something was wrong when the teen's hearing began to go when he was 14.
It transpired he had avoidant-restrictive food intake disorder (ARFID), and his subsequent lack of nutrition wrecked his optic nerve, causing a condition known as nutritional optic neuropathy (NON).
His mum, who is in her 40s, said the loss of his hearing and sight means he has no job and no social life.
She said: "We couldn't believe it when we were told what had happened. We are told the damage is irreversible. It's been a nightmare.
"His sight went downhill very fast - to the point where he is now legally blind. He has no social life to speak of now.
"After leaving school he got into college to do a course in IT. But he had to give it up because he could not see or hear anything.
"He would love a job - but he has not been able to find anything he can do. I had to quit my job in a pub. I now look after him full-time."
Reflecting on how his problems all began, the mum said he only ate Pringles, sausages, chips, processed ham and white bread since the age of seven - though this unhealthy diet didn't manifest itself through obesity, as you might typically expect.
She said: "The first we knew about it was when he began coming home from primary school with his packed lunch untouched.
"I would make him nice sandwiches - and put an apple or other fruit in - and he wouldn't eat any of it. His teachers became concerned too.
"His brother and sister have never stopped eating. They love everything. But he was just as fit and healthy as them.
"He has always been skinny, so we had no weight concerns. You hear about junk food and obesity all the time, but he was as thin as a rake."
Despite the damage caused by his diet, the teen is still living primarily off junk food.
His mum said: "He is taking vitamin supplements - but his diet is still pretty much the same. When he was having counselling we managed to start him on fruit smoothies. But he's gone off those now."
While the family wish to remain unnamed, they have agreed for the case to be reported in the journal Annals of Internal Medicine to raise awareness of ARFID, as well as the importance of nutrition for good eye and ear health.
Chosen for YouChosen for You
Most Read StoriesMost Read