A GP who was struck off for his tendency to jump to an early diagnosis and become fixated on it will have to justify why he should not be banned from the NSW legal system, after the state's highest court found he could not or would not accept its rulings.

Michael Van Thanh Quach, who has narcissistic personality disorder, has been appealing the decision of the Health Care Complaints Commission (HCCC) to cancel his registration for seven years since the ruling was handed down in 2015, following patient complaints that he had wrongly diagnosed asthma, pregnancy and a urinary tract infection, among other conditions.

He administered adrenaline to a patient who was suffering a mild allergic reaction, causing her to black out and hyperventilate, diagnosed another with a urinary tract infection despite no urinary symptoms and terminated his relationship with another patient when she complained he had given her the wrong vaccine, the NSW Civil and Administrative Tribunal found.

"The doctor-patient relationship relies on mutual trust," he wrote to her. "You have expressed a lack of confidence to me …"

He told a 20-year-old patient who presented with vomiting that she was probably pregnant, despite her protestations that she was a virgin and was menstruating at the time, and that her earache was likely caused by smoking, although she said she had never smoked.

When a child who the Children's Hospital had recommended for whooping cough testing came to the medical centre where Dr Quach practised, he refused to perform the test and instead proclaimed he had asthma, sticking to this diagnosis even after the boy's father said he had previously tested negative to it.

A psychiatrist who gave evidence to the HCCC hearing said Dr Quach's premature diagnostic conclusions could be put down to his inability to self-reflect and narcissism, and the characteristics of narcissistic personality disorder had the potential to impair his clinical judgment.

Andrew Petheridge said people who suffered from the disorder were apt to make incorrect interpretations and were always suspicious. They jumped to early conclusions and remained fixated on them. They dismissed any person who was critical of them as inferior and unworthy of the criticising conduct.

The NSW Court of Appeal drew its own conclusion on Dr Quach on Tuesday when it threw out his latest motion as vexatious and an abuse of process and took the rare step of asking him to show cause why he should not be banned from making further claims in relation to the matters.

Dr Quach's litigation has been rattling around the court of appeal for nearly two years, as he has variously sought to nullify the HCCC's decision to cancel his registration, to disqualify certain judges from hearing his case and to ban the court's registrar from hearing any matters involving medical practitioners on the grounds he is not a "senior judicial officer".

"The problem which confronts this Court and the respondents is that Dr Quach will not or cannot accept that his claims for judicial review ... have been determined by this Court and that further attempts to re-litigate those claims are both futile and an abuse of process," Justice Fabian Gleeson said in his reasons.

"It seems very likely that, unless a vexatious proceedings order is made, Mr Quach will persist in seeking to re-open orders made by this Court. The consequences of further applications inevitably will be inconvenience, unnecessary expense and a waste of the Court's limited time and resources."

Thirty-three people have been prohibited from making claims under the Vexatious Litigants' Act since 2008.