The U.S. Food and Drug Administration approved the drug rilonacept to treat a group of rare diseases causing rash, fever, chills and joint pain.

Rilonacept, marketed under the name Arcalyst by Regeneron Pharmaceuticals, received marketing approval for the treatment of Cyropyrin-Associated Periodic Syndromes, including Familial Cold Auto-inflammatory Syndrome and Muckle-Wells Syndrome in adults and children ages 12 and older.

The familial cold syndrome is an "orphan" hereditary disease affecting only about 300 people in the United States, 90 percent of whom can trace their ancestry to a single person who came to America in the 1600s, the University of California's San Diego School of Medicine said Wednesday in a news release. Symptoms can be triggered at any time by exposure to cold temperatures, stress or exercise,

The drug is based on a discovery by Dr. Hal Hoffman, a professor at the medical school, who identified the genetic basis of the disease as a mutation that causes alterations in the protein cryopyrin.

Copyright 2008 by United Press International