A new review is to take place into the death of a teenager with autism, who died after being given anti-psychotic medication.
Oliver McGowan, 18, from Bristol, was being treated for a seizure at the city's Southmead Hospital in 2016 when he was given olanzapine to sedate him.
His parents say a finding that the death was "potentially avoidable" was removed from a previous report.
NHS England has announced an independent review into the death.
The learning disability mortality review (LeDeR) into the death will be overseen by Dr Celia Ingham Clark, England's medical director for professional leadership and clinical effectiveness.
Mr McGowan's parents, Paula and Tom McGowan, said they repeatedly told medics he should not be given the drug because he had reacted badly to it in the past, and because he did not have a mental health diagnosis.
The drug caused his brain to swell severely and he died in intensive care.
Last year the coroner ruled the drug had been properly prescribed.
Mr and Mrs McGowan have said they suspected the NHS of a cover-up over the death, after they discovered an early version of a report, published as part of a previous review, found his death was "potentially avoidable".
They said a Freedom of Information request, used to access emails discussing changes to the report, revealed this information did not appear in the final version after an intervention by CCG staff.
Ms McGowan said the new review was "a huge positive" and a "leap forward".
It is understood that the NHS Bristol, North Somerset and South Gloucestershire CCG rejects the accusation that staff sought to alter the report.
A spokesperson said: "We deeply regret that the McGowan family's experience of the LeDeR process was so unsatisfactory and distressing for them.
"We will of course participate fully and transparently with the review in whatever way is required."