Jacob Madgin has hyperekplexia, known as startle disease, which causes his body to overreact to shocks and make his muscles tense up.
His father Allan, from Wallsend, North Tyneside, said some seizures and spasms could lead him to choke as his throat went rigid.
Nevertheless, Jacob is starting school on Thursday.
He is attending Battle Hill Primary thanks to an improvement in his condition brought about by muscle-relaxing drugs.
The neurological disease was diagnosed when he was eight months old - being breast or bottle fed would cause him to spasm if his nose touched the teat so he had to be tube-fed.
As he got older, other incidents such as seeing a dog or horse could send him into a spasm which could stop him breathing.
Mr Madgin, 56, said he had "lost count" of the number of times Jacob had been rushed to hospital.
Mrs Madgin, 48, said: "Starting school is a massive step, but it is a natural progression that you would expect for any boy.
"The big thing is the choking risk, but the school has been absolutely brilliant."
Prof Robert Harvey, from University College London (UCL), who is involved in research into hyperekplexia, said the number of people affected was unknown, but he believed it was underreported and in some cases misdiagnosed as epilepsy.
He said it had been linked to infant death and placed a "great burden" on those affected.
"You can imagine for this little lad, these triggers cause great stiffness and it can affect breathing, so life is very difficult for people who suffer from it," he said.
He and colleagues from UCL and Swansea University are researching possible causes of the disease.
A four-year-old boy with a rare genetic condition, which can literally leave him scared stiff, is starting school.