Former patients of neurologist Dr Michael Watt called for him to be reinstated yesterday at a protest outside the Royal Victoria Hospital.
Around six patients gathered signatures for a letter to be sent to the Belfast Trust, with more than 300 signing up so far.
Concerns over misdiagnosis prompted the largest ever patient recall in Northern Ireland last week. Over 2,500 patients will now attend 200 special clinics in the next three months.
Christine Lynch (55), from Belfast, helped organise the protest. She was diagnosed with multiple sclerosis by Dr Watt in 2005.
She said many patients would defend him "to their dying breath" and that the group was considering a class action lawsuit against the Belfast Trust over the matter.
She said: "I had been sick for about 12 years before my diagnosis.
"No one believed me that I was sick and I nearly went out of my mind. Not only did Dr Watt believe me, he put me on treatment within a year."
Rhonda O'Neill (44), from Magherafelt, has been a patient of Dr Watt for eight years.
She has a rare condition called autonomic neuropathy which affects her organs.
"It's quite difficult to diagnose and treat, but Dr Watt has been fantastic and he has tried wonderful treatments that have helped and made such a difference," she said.
The rarity of her condition means she now has to go for treatment in King's College in London.
Julie-Ann Fitzsimmons (46), from Lisburn, has been a patient of Dr Watt's for 13 years.
She was diagnosed with multiple sclerosis in 2005.
She said: "He has provided excellent patient-led care. I think the recall is absolutely ridiculous, it's scaremongering and extremely distressing for any patient and their families, and especially for Dr Watt."
"I gave up nursing because of my condition. Not having a consultant that knows me now is very concerning."
Jane McMahon (43), from Belfast, was also treated for multiple sclerosis.
She said: "My first neurologist wasn't too keen but Dr Watt started me on a treatment that's helped. I'm very concerned about changing doctors. I was in hospital quite recently with pneumonia and there was no neurologist available to decide if I should stay on my medication.
"I had to make that choice myself while I had an infection."
Dr Watt has been suspended from duties by the Belfast Trust, with interim restrictions imposed on him by the Medical Practitioners Tribunal Service while the General Medical Council prepares a case against him.