The patient, who was not identified, sought medical treatment in Hong Kong on April 6, when he appeared mentally deranged and showed other psychiatric symptoms, Hong Kong's Hospital Authority said in a statement.
He has since received intestinal surgery and is now critically ill, the statement said. Tests were inconclusive but doctors suspect the patient has contracted variant Creutzfeldt-Jakob disease — believed to be contracted by eating animals infected with mad cow disease — based on clinical symptoms, the authority said.
The man is ethnic Chinese and was born in Britain, Health Department spokesman Lee Ying-ming said. He lives in London and visited Hong Kong with his family on April 4, Lee said.
The man was hospitalized two days later when he felt dizzy and "behaved oddly," Lee said.
Mad cow disease, or bovine spongiform encephalopathy, is a degenerative nerve disease in cattle.
Eating contaminated meat products has been linked to the rare but fatal variant Creutzfeldt-Jakob disease in more than 150 deaths. The outbreak, mostly in Britain, peaked in the 1990s.
Hong Kong recorded a confirmed case of the human variation of mad cow disease in 2001.