Alex Keenan, 37, was diagnosed with Guillain-Barré syndrome in June and his twin sister said his condition has "deteriorated at a frightening rate".
Leanne Moore said: "He is paralysed from the neck down and unable to speak. It is absolutely heartbreaking."
The rare condition affects about 1,200 people in the UK each year.
Mr Keenan, a former gardener from Port St Mary, was transferred to the Walton Centre's Intensive Care Unit in Liverpool after spending weeks in intensive care in the Isle of Man.
Guillain-Barré syndrome sees the body's immune system attack part of the nervous system.
He has now been diagnosed with Acute Motor & Sensory Axonal Neuropathy (AMSAN) - a severe case of the autoimmune disorder.
So far about 150 people have donated more than £4,500, which the family said will be used to help finance weekly visits as well as buy equipment.
Mrs Moore said: "We are so grateful for this support - we are trying to be with him at least two or three days a week and it will make a massive difference.
"Alex is an extremely talented artist and a gifted musician who devours books.
"He is very curious about the world and right now all his thoughts are trapped inside his head - he must be so frustrated that he can't communicate with us or hospital staff.
"My brother is obscenely intelligent and specialists have stressed the importance of keeping him mentally stimulated.
"At the moment we could be looking at years of rehabilitation - that's if he does make any type of a recovery and that's not even certain at the moment."
•The exact cause remains unknown
•             A rare condition of the peripheral nervous system
•The key symptom is the rapid onset of muscle weakness
•Often leads to the paralysis of the legs, arms, and even the muscles which control breathing
•60% of people develop the condition shortly after having a viral or bacterial infection
•Most common in adults between 30 and 50
The family of a "talented artist and musician" left paralysed because of a rare condition have launched a appeal to aid his recovery.