A patient has died in a study of an experimental gene therapy, the US Food and Drug Administration reported on Thursday. The agency said it was investigating the death to determine whether the treatment was to blame.

The case could be another setback for gene therapy, a field with a troubled history and numerous treatment failures, including the death of a teenager in 1999 in an experiment.

The new therapy being tested, made by Targeted Genetics, of Seattle, is a virus-based product injected directly in the joints in hope of relieving active inflammatory arthritis. That chronic condition can affect multiple joints and organs, and it is quite different from the wear-and-tear arthritis that commonly occurs with aging.

The patient became ill soon after receiving a second injection, the drug agency said. The date is not exactly clear, but the illness was recognized as a “serious adverse event” last Friday, and the agency immediately suspended the study. That means no more injections can be given. The patient died on Tuesday. Targeted Genetics and the drug agency said they would not describe the patient’s symptoms or the manner of death until the investigation had been completed. The company and the agency emphasized that it was not known whether the treatment had a role or the death was a coincidence. The agency said the timing was cause for concern.

H Stewart Parker, chief executive of Targeted Genetics, said: “The patient was dosed one dose and had no issues and came back several months later and coincident with the dosing had an SAE”. SAE is an abbreviation for serious adverse event.

Parker said the company had used the same type of virus to carry various genes into more than 500 patients and had not seen similar problems. “These patients are all on several different medications,” she said. “They certainly have disease characteristics.” The drug agency said it was reviewing all other studies using the same virus, which is called an adeno-associated virus, though it had not heard of similar problems.

Dr Theodore Friedmann, a professor of pediatrics and head of the gene therapy programme at the University of California, San Diego, said the AAV system used in the experiment was widely regarded as safe.

But, Friedmann added: “We’ll probably come to learn it does some harmful things in some settings”.