Rat bite fever misdiagnosed as Rocky Mountain spotted fever.

A patient who had been exposed to ticks and who had also been bitten by a laboratory rat developed fever, headache, and a rash. He was treated with chloramphenicol for Rocky Mountain spotted fever, and recovered. Blood cultures, however, grew Streptobacillus moniliformis, a causative agent of rat bite fever. The case report illustrates the clinical similarities between rat bite fever and Rocky Mountain spotted fever.