Huntington's is a progressive disease that causes a progressive breakdown of nerve cells in the brain. It impacts a person's functional abilities and usually causes movement, cognitive [thought] and psychiatric disorders.
Fire investigator Bruce Irvine told Fairfax the main factors of the accident were smoking and the man's choice of clothing.
"There was nothing deliberate about his actions other than he was smoking."
NZCare Disability general manager Vicki Stewart told Fairfax the company was "deeply saddened by this incident" and that support was being given to the family members and affected staff.
"We are working with the New Zealand Fire Service to determine any learnings that can be gained from this tragic incident."