Ledge Light Health District has investigated an incident of contaminated red snapper served at an unidentified area restaurant that led to a serious and rare illness in a 36-year-old man.

Russ Melmed, epidemiologist and supervisor of health education and community outreach for Ledge Light, said the man was hospitalized at Lawrence + Memorial Hospital in New London two days after eating the fish at the end of April. He was diagnosed with rhabdomyolysis, a condition characterized by swelling and breakdown of skeletal muscle and risk of kidney failure, and given dialysis treatments, he said. The man spent almost three weeks at L+M. The cause of the illness was identified as Haff disease, a rare and poorly-understood disease.

Melmed said that after Ledge Light was notified of the patient’s condition, the agency visited the restaurant where he consumed the fish. It took possession of six other frozen red snapper that may also have been contaminated, he said.

“It could be just the individual fish, but out of an abundance of caution we embargoed all the fish in the freezer,” he said.

He declined to identify the restaurant or provide further information about the patient. The contamination is caused by a toxin in the fish and is not believed to be the result of any negligence on the part of the restaurant, he added.

Mike O’Farrell, spokesman for L+M, said the patient is no longer at the hospital. He declined to provide further information, citing patient privacy statutes.

There have only been about 30 recorded cases of Haff disease in the United States, Melmed said. The current case appears to be an isolated incident. The state Department of Public Health and the U.S. Food and Drug Administration have been notified, Melmed said.

Maura Downes, spokeswoman for the state Department of Public Health, said the health department would only take action if there was more than a single case of the illness. The toxin in the contaminated fish is believed to occur when fish is not kept cold enough after being caught, she said.

Ledge Light provides public health services to New London, Groton, Waterford, East Lyme, Old Lyme, Ledyard and Stonington.

 j.benson@theday.com